Duplicate modal error messages
Some modal error messages (at least OpenPGP and Avahi, see screenshot) are popped-up more than once over long-ish periods of time (or sleep/suspend cycles). Despite the error not being directly actionable nor blocking, which would suggest that a message dialog is not needed, the modality of the dialog makes it hard to close, as they need to be closed in reverse order of their apparition.
An immediate fix would be to pop-up the message only if no other dialog is already displaying it, or otherwise just ignore it.
A better fix would be to capture those error in the state of the associated accounts, and display them as notification somewhere in the roster. This would be much less intrusive, while keeping the warnings visible.