Yes I brought this up before here. That is why the signature previews also show the file size, so you can determine which ones will fit in with whichever forums rules there are.
Yep. I spent 3 months developing the custom signature system just to deal with tfw2005's somewhat arbitrary enforcement of this rule (their concerns are not solely technical--they allow unlimited sig size for a membership fee). Unfortunately, you can't cram too much into 40k, so you pretty much have to turn off everything but the fun facts, and use a plain background (you might even have to use a custom solid background if you're still going over the limit).
But you don't have to let them spoil all your fun. You can have as many custom sigs as you like, so you can have a bare bones one for them, and a 14-pager for everybody else.
Oh, and some other bugs came up, so I haven't fixed the updating issue yet. Should get to it tonight.