@Richard You raise a good question, particularly for forums and blogs, where the rules of the game are determined by the people who run them. My article’s focus isn’t on forums or blogs (though I believe that both would benefit from many of the ideas in the article), but rather on online magazines and, really, the few of them that take pains to “vet” articles. So, credibility is rarely an issue.
Motives and intentions seem beside the point to me for the type of articles I discuss. The thing to judge is the article itself and its issue. My advice is to stay focussed on the issue and move it forward, rather than getting sidetracked trying to determine the motivations or intentions of other people in the discussion area. Attorneys, judges and juries have an entire trial to present cases, pro and con, to determine, among other things, motive. Cases built purely on motive are usually called circumstantial. Too, the the purpose of a trial is usually that there is good reason to believe that someone has done something wrong, and our goal is to figure out who. That’s not the purpose of a magazine article, and I’ve tried to point out that when we take trail-like adversarial positions, the result is usually unproductive for everyone involved. If you think an article author is duplicitous, in that their article is a case of plagiarism, your best bet is simply to contact the editors of the magazine (providing proof, of course).