1, 2: Removing CQ vote is the way to cancel CQ attempt. Since you voted CQ+2, so your vote had to be removed.
To be clear: we are aware this kind of interaction with CQ doesn't allow for awesome UX. Sorry for this :(


3. The CQ status link you've shared also says:
"(Committing failed: Error submitting change .)" which means Gerrit flaked. CQ does retry submits, but apparently gerrit flake was persistent. Since Gerrit error reason wasn't clear to CQ, CQ aborted attempt.

btw, wrt to 1,2: I am not sure but it could be possible to add text message XXX in 
"""
Commit Bot on behalf of Primiano Tucci
Patch Set 1: -Commit-Queue

XXX
"""

what XXX would make it better?

tandrii@: The CQ should simply both set the label and post the message in the same API call. Right now, _cancel_attempt makes two separate API calls: one via _reset_cq_votes, and the other via _add_comment. If those are combined, the UX might be a lot better.

What you suggest is clearly feasible, but there are more special cases then:
1) There could be more than one user voting on CQ label. Perhaps then msg can be sent for both calls.
2) If removing vote fails, CQ still needs pots a message in order to stop processing a CL.

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