While I don't get the author information block displayed on this page, I assume (based on the link on my own page and the itemID of this page) that the link is 
https://www.chessvariants.com/index/managefiles.php?itemid=MSphantom
which gives me the error:

The directory  /membergraphics/MSphantom/  does not exist.

Trying to navigate directly to the folder also fails.

and if you'll allow the humble 8x8, you can test out that endgame:
https://www.chessvariants.com/membergraphics/MSinteractive-diagrams/EGT.html?betza=WAD&name=Champion&img=champion
(I really like this thing; thanks H.G.!)

I noticed that the Champion's Piececlopedia page has an incorrect diagram (due to the new marker code).  I'll fix that and add a link to the 8x8 checkmating practice after work today.

I don't understand the phrase "Draws are possible; stalemates are not."  But in the addendum, point 3 is pretty clear:  

If you cannot make a move during your turn, you lose.

So the Vf1xf7 move H.G. brings up is actually a winning move.

I get that the Templar is a knight plus captureless-ox, but the other pieces that move like a "Templar but not as an Ox" should instead just say they move like a knight or <whatever>; I think that would be substantially clearer.

The Giraffe's description wasn't clear to me, but the movement diagram mostly fixes that.  But, is the Giraffe blocked by a piece diagonally adjacent?

Very nice!  I was considering attempting this, but using diffs instead of saving the entire revision (but with the final, and perhaps various intermediate versions, saved in full so that lots of diffs wouldn't need to be processed to display a page).  That might be something to still try, if the size of the revisions table is a concern.

I can't see revision counts from any of the Edit links that I know about (but can in this New Submissions list), nor a link to the revisions.php script.  The editor-use Edit page has text concerning revisions, but the link doesn't work, and the author-use Edit page hasn't been changed recently.

And a separate issue (for editors): does loading the Edit Index Information (for editors) page take a long time to load the inventor/author dropdowns for anyone else?  If so, I'd like to move those into a new script, so that categorization, primary/secondary links, etc. and approval can be done more quickly.

@H.G.,

The "missing description" refers to the "Short description" in the first page of the member submission process.  That field is not available (at present) from the edit index information page (either authors' or editors'); instead the "What's new" field is available.  Editors can edit that field through the edit links page, so for now you can just request the change.

The pawn promotion zone isn't entirely clear, but I suppose it's the four squares on the mentioned diagonal e8-h5 together with (when a pawn captures diagonally due N) the diagonal f8-h6?

I'd suggest moving the "motivational" setup to the notes.  Having it in the introduction, at first read I thought that was your game!

I fixed a bug on this page: the query ordered by CreationDate but tried to group for display based on ModifiedDate; I think here having the query order by ModifiedDate makes more sense.  However, there are a handful of pages here with ModifiedDate=0000-00-00, which get tacked on at the end.

@Fergus, I'm not sure what causes a page will have this degenerate ModifiedDate?  Even your test page that has revisions in the table suffers that affliction.

I'd guess it's seeing a 2-leap followed by a bishop move inward as legal?  And that doesn't matter for the Aanca because those same squares can be reached legitimately by a shorter path.

Ah, so I was wrong about the promotion zone!  Glad to have that clarified!

The Subject entry box is wider than my screen. When I press Preview, make some changes, and press Preview again, the preview is empty. (This was before logging in, if that matters.) There's an Edit and View (and [*]) link on the preview that doesn't work (and probably shouldn't be there). When I draft a message and then try to log in, I get an error along the lines of "You must be logged in as the original author to edit a comment" (this was after Preview, in case that matters).

We should add

1. a link to a markdown guide; since Parsedown uses github-flavored markdown, maybe https://guides.github.com/features/mastering-markdown/ ?
2. possibly a short list of common markdown?

bold emph emph, emph

header

header2

Please see the thread "The new editcomment.php script" for discussions around the comment input form.

This looks pretty neat! Unfortunately I don't have Zillions to play the implementation; any other editors have it want to have a go before reviewing?

Done.

I don't remember the What's New and Description ever being the same...? The What's New is generally not a good description of the page, just pointing out what has changed on the page ("added example" or "modified endgame conditions", for example).

As to why Descriptions historically haven't been easy to edit I can't say, but Fergus seems to have recently expressed interest in changing that.

So there is an item ID, a summary and a description. The item ID determines the URL (and I will never repeat the mistake to make that very long!).

Right so far.

The index will list item ID + description, the comment headers will list summary + description. Apparently summary and description are set to the same text when first submitting a new article? It is the summary that can be controlled by the author through the 'Edit index information', as 'Item name'.

I don't think this is right.

The Summary is also called the Item Name, and the latter name is perhaps clearer. The Description is a one-sentence(ish) blurb. The ItemID is a unique permanent identifier, which the URL is also based on. Then there are Index Entries, with a Link Text and Link Description; these are used on search pages (except What's New, which has its own description), and the header on comment threads use the Item Name and the Link Description (???).

When you first submit a page, you provide an Item Name and a Description. An ItemID is created based on that Item Name (generally with a prefix MS, MP, etc. and with spaces replaced with hyphens, etc.). The ItemID is meant to be a permanent unique id, and the URL for the page is based on this ID as well.

The Description that you provide when you first submit a page just populates the initial Index Entry, together with the Item Name. Most pages will only ever have this one Index Entry, but you can have more; see in particular the Piececlopedia, where a piece with multiple common names is given and Index Entry for each name, for ease of discovery. (We also distinguish "Primary" index entries, and the query can filter down to only those primary entries if you don't want the duplicates.)

You can update the Item Name. This will not update the ItemID nor URL (because those are meant to be permanent), so these can diverge. Also, changing the Item Name doesn't update the Index Entry, which might be a little confusing. I think users can't add index entries (perhaps to prevent exploiting them for greater visibility), but updating them may be made available.

I would also like to have descriptions changed for the following pages...

done.

The board graphic has two wizards behind the royals, while the ASCII board has two revealers.

This is interesting. I'd like a more descriptive name for the variant, but I don't have one to suggest right now...

On fools, the paragraph seems to mean that neither fools nor kings can move such that the fool "attacks" the king. The convoluted language comes I think in part because the fool cannot capture any pieces at all, and so the author is trying to avoid the word "attacks" or its variations.

Several of this author's pages say just "castling is free," which I can only attribute to the historical rule? I haven't read all of them to see whether they elaborate somewhere.

I'm also confused about the hunter movement:

...The hunter can't jump over any agent when it's travelling either diagonally or orthogonally. When travelling purely orthogonally, the hunter can never even jump any agent located on squares of opposite color. ...

The second sentence here seems to be redundant, unless diagonal movement is supposed to allow jumping over opposite-color squares?

An observation: this game is not symmetric.

I think it is mirror symmetric, and I think the confusion stems from "left for white and right for black". I believe the author means "files earlier in the alphabet" for both, and the different handedness comes from players generally sitting on opposite sides of the board.

(Imagine pawns being wrapped around king's starting position)

In the starting position, remove the major pieces. Treat the pawn row as a cellophane film, and pull it tight around the king, "sticking" the e pawn where it is. The d and f pawns also get stuck where they are, the c pawn gets pulled down into d1, the b pawn further pulled to d0 (offboard), and the a pawn down and around into e0. Similarly for the right half of the pawns, and now the position of the pawn relative to the king is the same direction that that rank's pawn grants power to the king. I do think this is a good mnemonic; anybody good at a quick animation? :P