An update. Turns out mibbit will stay banned from oftc.net, where our IRC channel for chat is.
If you want to use chat in a webrowser you can use webchat provided by oftc.net themselves:
https://webchat.oftc.net/Enter your nick and the name of the channel: #lor
or you could use an IRC client and use the following info to connect:
server: irc.oftc.net
channel: #lor
you may use secure connections on port 6697
As for what IRC program to use, I've used
XChat for a while. It's free for Linux.
You can also try
Chatzilla as an addon to Firefox.