I heard that some people with SourceMod on their servers were experiencing the same thing I am, with the neverending music, missing "X killed Y" messages, and gibberish in the consoles. So I tested to see what was wrong by disabling some plugins. And I found the offending plugin (at least, for me), in the
Perkmod plugin. Apparently, whenever text is entered in the chat box (consoel-related, like the Advertisements plugin or any notifiers, the console gets bugged with the nonsense. And when I turned off Perkmod, the nonsense went away.
But I heard that it was happening on servers not running Perkmod, so I'm curious as to whether it has something to do with the way they're programmed to work with SM (I'm extremely noob at programming), or if they're just a random bug in the plugins themselves.
If it matters, I was running one of the 1.2 stable SM versions before the CC update broke things, and once they did, I got a 1.3 snapshot, so I switched versions, if it matters.