Max characters per post is 20,000. Default was 10, but back when I was a lot more active I ran into it once or twice and decided to up the limit. 20,000 is a damned lot of characters, which I'm not going to help you visualize here... but you can do 20000 bytes in the
lipsum generator. To be clear, 10k is more than anyone
should need in forum-ish discussion, and if you're breaking the 5k mark on a forum post you probably need to stop writing and give George Orwell's "Politics and the English Language" a bit of your attention.
As for "walls of text" being 5 or 6 posts of things not relevant to your interests ... yeah, that's annoying. But you can pretty much skim a post in like 5 seconds and find out whether it merits further reading. So ... 6 irrelevant posts ... that's what, 30 seconds of your life? I've spent more than that typing this reply >_<.
On the topic of larger sigs... I've experimented with 500x125 and 125x125 avatars in the current layout (and given them out as contest rewards to a couple people). They're pretty reasonable in those circumstances. I'm not sure that 150px height isn't a bridge too far for me, and I like the 4:1 aspect ratio on them (they were originally limited to 400x80, if you remember back before my reign of terror started). Avatar and sig limits can be adjusted after the migration though, so that's a deferred decision.
Threaded and nested conversations... my best answer is this:
I invite any discussion regarding layout and feature decisions on the forums, but spoiler tags are a closed issue that we're pretty much in agreement on. Not happening, let's move on.
On the related topic of remake-series (like ... any rehash of anything, at all)... yeah, that's a tough one. I guess it really depends on whether everyone's seen it or not, and how different it is. If they follow very similar lines (like it sounds like you're talking about), I think it'd be ok to talk about subjects that have already occurred in the remake. So like, if shinji fell down some stairs in episode 17 of the original evangelion, and Asuka pushed him down the same stairs in episode 17 of an eva remake, that'd be fair comparison grounds, but only consistent with our other spoiler rules for when you can talk about something. That'd be my take on it anyway. I doubt people who're watching dbkai are going to go back and slog through twice as much badly-paced dbz to find out what Roshi was doing when Goku was making a genki-dama, you know?