Hi there! Sorry to hear that you're experiencing problems with larger avatar sizes. However, given the case, I don't intend to rework the code behind the profile section. If you look at the vanilla prosilver style, you'll see that it has the same problem--just on the right of the post instead of the left. The issue is that prosilver has an inherent semi-liquid layout, so placing the profile section to the left as I've done makes everything shift when the bug comes up, whereas prosilver's layout means that while the avatar itself overlaps the boundaries of its box, it does not move anything else in doing so.
Essentially, given that this bug is inherited from the original prosilver style, I don't feel it is an urgent issue, and as such I don't currently plan on fixing it. If this is an issue for you, I'm afraid I have to suggest that you reduce the maximum size permitted for user avatars, or, alternatively, pick a style that displays profile information to the right of posts, since that will largely negate the issue. (I don't mean that in any kind of sarcastic or mean way, by the way; I hope you don't take it that way.
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Thanks for letting me know about the search bar dropping off the header--I honestly missed that when testing the style. Off the top of my head, I don't know if I can fix it easily, seeing as the content of the box itself will vary from board to board, but I'll see what I can do about it for the next release.