Under certain conditions (IMAP account offline or not responding or ...?) it can happen that messages deleted from GMail accounts end up in my local wastebin rather than being moved to the configured wastebin folder on the server.
When this happens, they remain "greyed out" in the folder they originate from even when they have been removed from the local wastebin, for an indefinite amount of time (= I have to connect through the web interface to delete them there).

Sadly I cannot say how to reproduce the issue.

Reproducible: Sometimes

Steps to Reproduce:
1. Use a gmail account in a real-world usage scenario, which includes deleting (selections of) messages while syncs are going on, etc.
2. Notice unread/unseen messages signalled in the otherwise unused KMail Folders "account", that this concerns the wastebin, and also notice that those same messages are greyed-out in their original folder
3. empty the local wastebin in an attempt to remove those greyed-out messages

Actual Results:  
Local wastebin is emptied but messages apparently remain on the server, untouchable.

Expected Results:  
In fact, I'd expect that "Move to wastebin" and its keyboard shortcut move messages to the configured wastebin, or not at all (i.e. defer/queue the action) when that is not possible immediately, for whatever reason.

It would be OK to post a dialog "Cannot move message[s] to the configured wastebin, $FOLDER, because $ERROR. Do you want to move it/them to a fallback wastebin?". At least the user knows what's going on like that.

I'm marking this a major issue because of the unpredictable non-respect of a user setting.