Mysterious IDv2 tags that MP3tag can't find?

So here's the skinny.

I've got a whole stack of files that some genius tagged like this:

http://i.imgur.com/gi5X2cK.png

Should be basic to go into mp3tag and have it batch-overwrite "various artists" in the artist field with the actual artist name from the comment field, right?

However, when I load the file into mp3tag 2.72...

http://i.imgur.com/taMosUm.png

...it can't see the comment field. It sees the other fields, no problem. But not comment. I've been poking at this for a bit now, trying various permutations of fucking with the tags, and mp3tag just continues to miss the field completely. It's entirely possible that I've missed a configuration option somewhere, but this seems like the sort of thing that the software should pick up by default. I dunno.

Anyone got any advice?

You should check the settings in
Tools>Options>Tags>Mpeg
Read and delete all tag versions
Write only V1 and V2
If you have problems with sometimes visible and sometimes invisible fields, play around with settings for reading APE - perhaps (overwriting) data is stored there.

Definitely hadn't thought of that, giving it a go...

...no luck. Thanks, though.

What do you see when you press ALT + T or

View - Extended Tags

If you still don't see it, care to upload one of these file so we / Florian can have a look?

Now we're getting somewhere. It's apparently filed what I see as a comment field outside of mp3tag as "COMMENT MUSICMATCH_TRACKARTIST"

So that's the field that has the info I need to replace the ARTIST field with.

e: Now I've got a column I'm oh-so-cleverly calling comment2 that shows that field. Now I just need to find a function that'll let me punch in the data from one field to the other.

Use an action of the type "Format value" for COMMENT
Format string: %COMMENT MUSICMATCH_TRACKARTIST%

You can try the same with the function Convert>Tag-Tag

Tag to tag has properly moved the data into the artist column.

I think we can mark this one solved. Thanks for helping out, everyone.