Discoveries in the process:
1) (obviously) everyone with write access to the community also has write access to any fic's tags. I followed the standard IcedarkElf set in the Magical Vanishing Post (assuming I'd done it correctly the first time that is, and if not, well, they're easy to change).
2) The tags feature won't allow the underscore character at the start of a tag, which means that ____ero__sennin got truncated to erosennin in order to be able to be tagged.
3) Since I'm not a maintainer there's nothing I can do about the tags not showing in the current community view, but if anyone wants to sort by tags, here's the URL that will always get you to the tags listing:
http://www.livejournal.com/community/thirtyforthree/tag/ It's a lot handier than memories because you don't have to click back and forth all the time; it assembles everything with that tag in one handy list.
From here on out, everybody tag your own, okay? It was easy for me to tag this time because basically I knew everything that wasn't mine or IcedarkElf's wouldn't be tagged. Later on, since the community view doesn't show things and the tag feature doesn't let you search for things without tags, it won't be nearly as easy for one person to play catch-up. Also, don't worry that it doesn't remember capitals - it never remembers capitals; everything gets turned lower case. Separate tags with commas, since spaces can be accepted within a tag name.
Here's the tag standard as I remember it from the post (and as I used it in tagging everyone):
1) LJ user name (converted to no-underscore form if need be)
2) Fandom name
3) Threesome name with no spaces (i.e. a/b/c)
4 to whatever) Theme # (use more than one theme tag if there's more than one theme in a post)
So for example:
This one (with two themes in it) got tagged by clicking the little blue Tag button at the top and entering edenfalling, harry potter, ginny/harry/draco, theme 18, theme 3 in the tag entry box at the bottom of the screen.
Since it alphabetizes the tags, the entry order doesn't really matter, but it's helpful to do them in that order to remember to get them all. (And Firefox's autocomplete saved me SOOOO much time when doing them assembly-line style too...)
(okay, I'm done rambling now. It was too late to start another fic but too early to go to bed. ^^;; Now it's late enough to go to bed...)