COPE Forum 4 December 2013: How should a journal deal with persistent complainers?

The topic for discussion at this Forum was ‘How should a journal deal with persistent complainers?’ Every so often a journal may get not one, but a series of complaints from the same source. These complaints may be directed at an author, an editor, or the journal in general. If these complaints turn out to be well founded, obviously there is a serious problem with the publication. However, we are aware of cases where a complainant continuously comes up with cases that turn out to be baseless. How should editors act when the complaints do not stop, get personal, and start humming around the community?