Another player and myself experienced this problem lately -- when typing T to chat, the letter "t" will appear in the chat and we'll have to delete that "t". I can't reliably reproduce it but I thought maybe somebody knows why.
Are all of you on 0.8.2 linux SDL? I heard the chat T issue was fixed in autobuilds (though SDL autobuild might have bugged fullscreen currently).
The console was also bugged at some point but not anymore so maybe also try git/autobuild?
To get an autobuild, make a backup of your Xonotic folder (the unpacked zip), then run one of the scripts in misc/tools/rsync-updater.
<packer> when i see martin-t's name my blood pressure increases
<[BOT]Hоtdоg> anyone here lives near martin?
<[BOT]Hоtdоg> will pay monies for shooting him
@martin-t, you are right. I play both the latest git and 0.8.2 (both SDL and GLX) so the problem was never consistent enough for me to tell what's going on. Now that you said it, yes, it was 0.8.2 SDL that has the problem.