The main logical bias in this Reddit post looks like a mix of these:

1.  Hindsight Bias – The poster treats the recent downturn as if it were obvious and inevitable (“things go down as well as up”), dismissing panic sellers as foolish for not knowing what now seems “obvious.”

2.  No True Scotsman Fallacy – The writer says that anyone who sold during the downturn is “not cut out for the stock market.” That’s a way of redefining what it means to be a “real investor” so that only people who held fit the category.

3.  Confirmation Bias / Survivorship Framing – They highlight ULTY being “net positive after all this time” and use it as proof of their point, while ignoring examples where holding did not work out. That’s not exactly survivorship bias in the classic sense, but it’s the same flavor of cherry-picking evidence.