While my idea of spoiler tags did include the inevitable details of spoilers in a non-spoiler section, I was actually mentioning them for other uses as well, such as putting images in spoiler tags (if the auto-resize couldn't happen), or putting long two-person discussions into tags (such as the ones that happen between, say, Yuki and Ryll), or anything else that could shorten a thread. I only read the Naruto and Bleach manga, which is so far ahead now, I can't even remember a lot of the stuff that happens, so posting spoilers for a series wasn't ever really an intention, except for in a case like Rebuild, where someone brought up the issue of comparing it to the original and whether or not that would be a spoiler.

As far as the sigs go, like I said, the 400 width isn't really the problem... it's just the 100 height. The majority of my sigs are 400x125, so I would be perfectly fine with that. 500x150 might be getting closer to too large, but it's nowhere near as bad as the, say, 600x400 or whatever some people use on a forum where there is no restriction.