Actually, this has been a case that I wanted to fix (currently there are exactly 200 composers, and so it's just enough; I deleted a few empty composer pages).
Anyway, there will likely be a fix for this soon, which would be a horrible and ugly (code-wise) hack (the Composer category probably hardcoded) but I guess it would work... currently thinking of a more elegant way to fix this, but that might not be possible.
Also, for page issues and most things that are temporary, it is technically much better to use the forums. This is because the forums are *much less expensive* in terms of computer resource usage. For example, if you edit a wiki page, the entire page has to be saved (this can sometimes be pretty big!), but in a forum only the new post is added. In this sense it is much more efficient to use forums if you want thread-like discussions that are temporary. Not to mention forums are much faster in the first place.
Wikis are better for information which need to be stored for a long time, like publication information, a detailed analysis of a piece, etc.