Awkward situation with editor several month after submission: advice
No, agreeing to peer review a paper for an editor would never cause the editor to have a conflict of interest.  A conflict of interest would only occur if the author somehow incentivized the editor to make a decision on a paper.  B providing (or failing to provide) a peer review is not an incentive to an editor, and it is unrelated to the decision on the paper written by A and B.

If C declines to handle the paper, some other editor will handle it.  This likely has no effect on you.  Probably it is best to do nothing for now.  I suggest that you not request C as handling editor in the future since they seem unprofessional.

If C were to directly violate the journal's policies, you might complain to the editor in chief, but it does not appear that has happened.  Don't complain now.


If C said &quot;I will not handle your paper because you did not complete your peer review&quot; then no, you are not being paranoid.  If C said &quot;You should not complain that your paper has not been handled because you did not complete your peer review&quot; then you are being paranoid.