Regarding the player list and being able to check it quickly, I think we could do well by just moving some things around, here's an initial take:

Current:
Alternate:

Some caveats:

• The current list style always dedicates enough horizontal space for two-digit numbers, here we'd only be doing that if there were 10+ players on the list
• I haven't thought about how to indicate muted players (currently there's an M on the left)
• Putting the gray + on the right end makes it too confused with the ms text, but I do want to do something with the gray +. Right now there are a whole bunch of things you might see there:
  • Red @ if you're the server and the client has a different plus version
  • Gray + if you're not the server
  • Teal + if you're the server and the client is running 1.24
  • Blue + if you're the server and the client is running 1.23
  • Gray ! if you're the server and the client isn't running JJ2+ but the client is running 1.23 and you're running 1.24, or the client is running 1.24 and you're running 1.23
  Not only is that difficult to keep track of, I'm doubtful it's all still useful. This is a system that predates JJ2+ v4.3, when 1.23 and 1.24 became fully interoperable. Personally the only thing I would actually want to know if someone's not running JJ2+, or possibly if they're running an earlier version of JJ2+ than I am (if clients even have access to that information).
• Most of the time you don't care about player ID numbers, but unfortunately they are useful for kicking/banning/muting/forcespectating/etc... maybe they could be hidden unless you're chatting something that begins in / or @?

ETA: some possible muted player designs