Sorry, I composed the above comment in a rush, and forgot to address the other questions you asked because I focused on the main objection.

Regarding other forums, the problem is that they offer only predictable feedback based on the ideological positions of the owners and participants. Depending on where I go, I can get either outrage and bewilderment or admiring applause, and while this can be fun and vanity-pleasing, it offers no useful feedback. So while I do engage in ideological rants and scuffles for fun from time to time on other forums, I've never bothered with making my writing there systematic and precise enough to be worth your time.

Regarding other thinkers, I actually don't think that much of my thinking is original. In fact, my views on most questions are mostly cobbled together from insights I got from various other authors, with only some additional synthesis and expansion on my part. I don't think I have any unusual epistemic skills except for unusually broad curiosity and the ability to take arguments seriously even if their source and ultimate conclusion are low-status, unpleasant, ideologically hostile to my values and preferences, etc. (Of course, neither of these characteristics is an unalloyed good even from a purely epistemic perspective, and they certainly cause many problems, possibly more than benefits, for me in practical life.)

The problem, however, is that on controversial topics, good insight typically comes from authors whose other beliefs and statements are mistaken and biased in various ways, and whose overall image, demeanor, and affiliation is often problematic. And while people are generally apt to misinterpret agreement on a particular point as a full endorsement of someone, and to attack a particular argument based on the author's mistakes and biases on other questions, I think LW has some particularly bad problems in this regard. This is because on LW, people tend to assign a supposed general level of "rationality" to individuals and dismiss them if sufficient red flags of supposedly general irrationality are raised.

Whereas in reality, on controversial and ideologically charged questions, there is much less consistency within individuals, and people whose rationality is sterling as judged by the LW public opinion (often not without good reason) typically have at least some horribly naive and biased views, while much good insight comes from people whom LW would judge (also often with good reason) as overall hugely biased and irrational. (The only people who maintain high standards across the board are those who limit themselves to technical questions and venture into controversial non-technical topics only rarely and cautiously, if at all.) So that on many questions, saying "I think X has good insight on topic Y" would be just a way to discredit myself. (When I think it isn't, I do provide references with the appropriate caveats.)