It's hard to know how common this is. But I have personally witnessed the L4 top folks talking down someones novel contributions as "this is nothing knew, you s

It's hard to know how common this is. But I have personally witnessed the L4 top folks talking down someones novel contributions as "this is nothing knew, you should have used L4, we did this stuff 10 years ago" and making a young researcher feel miserable. (IIRC the very same people also published a paper introducing the same novel idea in L4 some months later, but that's another discussion)