If there are a lot of people in the room, some mods can accidentally ban you, with the intention of banning someone else.
If you had any numbers in your name that could relate to you being underage, then that is a likely reason.
It also depends on your definition of "unreasonable"
If you didn't actually get a banned message then you weren't banned, and it was just the 'lag' in the room kicking you out, and not allowing you to log back in.
But the ban list is cleared - on average - every 24 hours, so try again tomorrow.