Here is how I use them:

BS is for just talking about stuff, and I *substitute* the term NonMusic if it's NonMusic BS, as a courtesy to members who like to skip the nonmusic threads. I don't equate BS with NonMusic, but I gather some do. For instance, discussions about the merits/lack thereof of Eminem would go under BS, but not NonMusic.

I use LyrAdd I'm contributing lyrics, and I'll do a separate post with LyrAdd if my lyrics are added into a thread about something that doesn't specify Lyrics Add. I do that as a courtesy to the folks actually getting the lyrics into the DT, and I do mention/link to the original thread. I don't see how you could put LyrAdd on just a posting within a thread.

I would agree with REQ being what is used for requesting lyrics or tunes or chords or whatever anybody wants to call the musical information stuff. I use LyrReq mostly because I can't read music, but I can read words, so I would never ask for chords or tunes, other than asking if X is sung to the tune of Y. But the English language problem is a point well taken.

I see no need to add any other prefixes; the obit threads vary, but so do the dead people and the members who cared about them. You could put something in the Newcomers thread about if posting about a death, please use RIP (which is shorter than OBIT and more close to the reality, which is usually a discussion of the contributions of the dearly departed, not merely an obituary). But some say "passed" and some say "died" and some say other things, the only one I recommend against is Passed, as so few people think that it means Died.

And I can't think of any other prefixes I've needed...