"Non-mainstream" physics is often equated to fallacies and fringe theories, including on this forum. Mainstream physics is rigorously categorized in specific historical scientific contexts, subject to unscientific beliefs of the time. As physics advances as a science, it corrects itself. What was mainstream to wrongly presume gets falsified by corrected mainstream knowledge.
Given these premises, are future corrective physics discoveries properly categorized as mainstream, in advance, or not?
[Thanks Buzz, for moving this to Meta, despite the rules. I'll use edit function to work around my lack of user powers. I've now edited the question for better clarity and detail. The following comments are what I can manage as a new member with a low reputation of 1.]
Its very confusing to newbies that a "mainstream" physics Q&A forum does not have the virtues of a Physics Forum as a friendly place, but rife with anonymous down votes and poorly supported deletions.
Social media like this can in fact do some good for open peer-review questions. Its Turing complete. Planck could just as well "question" Einstein with a fountain pen, or here, and it would be helpful peer review.
How did "reputation" become elevated to mainstream physics? Traditionally, Appeal to Authority was classed as a logical fallacy.
I see now Stack Exchange was created by Jeff Atwood, whom I know via Discourse meta discussion we have had. Great guy. His life has become increasingly occupied with unintended social consequences. Physics Stack Exchange is one more curious instance, in that physics and software Q&A and cultures are not really the same.
Atwood's Discourse forumware would be a better match to physics as a community that both answers questions and allow a Galileo and a newbie to co-exist more equitably, provided Moderation settings and Moderation were enlightened. Atwood said there is not much hope when a draconian whack-a-mole moderation culture takes hold, although architectural mitigation meta-analysis in Atwood's circle continues to seek solutions. Discourse Forums do not inevitably devolve into flamewars that only downvotes and deletions can prevent.
A reductio ad absurdum example of how this site is so weird-
Question about non-mainstream physics: "Is non-mainstream physics allowed here?"
Paradoxical Answer: "No, questions and answers about non-mainstream physics are not allowed here."
One cannot ask about what Newton got wrong (like absolute space and time, point masses, and so on), as its no longer be mainstream physics.
Comments below help answer "meta" questions facing this software platform as a basis for physics community.