I think I am talking about the same bug.
Sometimes when you log in you will not see yourself in the chat memberlist and also when this bug is happening and you type something, you will not see what you just typed after sending it to the server. Others see what you typed just fine. I'm not sure whether they see you on the online list or not, will get it confirmed next time it happens.
I've noticed it before the vicinity chat patch too and it's not specific to any chat channel. When this bug happens, all of the chat channels you are in will have the same issue. Relogging usually helps.