I asked for 3rd party involvement in a situation when I was dealing with an editor who was removing valid sources that were from a liberal-leaning source & replacing them with questionable right-wing sources. After I reverted the edits & engaged the editor, the editor kept repeating over & over that the reason the source was invalid,was because of the website from where it came. The editor ignored any arguments about the high quality of the writing  and citations in the source itself. When I engaged Wikipedia:Third_opinion, two uninvolved editors showed up in the discussion, identified themselves as neutral & uninvolved, reviewed the discussion, & engaged the other editor. The other editor immediately stopped ranting & there was no other issue with that editor, at least for that one article.