BitlBee <= 1.0 didn't have "account set" and allowed one to delete an account
and re-create it with new login settings if necessary, without losing custom
nicknames. Now, nicknames are connected to an account instead of just the
protocol, and they're flushed together with the account. So I added a warning
to make sure nobody accidentally loses any settings while just changing the
password. This will probably go after a few releases, since it's slightly
annoying.
