Just a thought: currently the chat screen (if you bring it up with Ctrl+M) automatically jumps to the bottom when someone exits/arrives/dies/talks/etc, and doesn't obey the scroll lock key. Could this possibly be considered as a feature?

I understand it's a game and not a chat client, but sometimes you want to see what was said (or linked) above the current bit of text
If it's difficult or problematic (i.e, if Scroll Lock status is managed differently on Macs/Linux or not at all on Macs, I'm not sure), then simply having a little checkbox at the top of the chat window for "Scroll automatically" (ticked by default) may be one way of keeping a consistent UI across all platforms
What do you think?