When a char is renamed by a GM  (the nickname changes, charid still the same) the char is somewhat broken in the bot:

Old nickname still member of the bot.
New nickname is not on the member list (since there is no Org. Msg. about joining and the roaster update doesn't seem to handle it).

When trying to remove the old nickname:
To [BOT]: !member rem OLDNICK
[BOT]: OLDNICK does not appear to be a valid character. You might want to erase this user.

When trying to add the new nickname:
To [BOT]: !member add NEWNICK
[BOT]: OLDNICK is already a member.

So I think the handling is broking by mixing the use of charid and nickname.