Signatures have been limited to lines of four or less for some time now, however, if certain vB code tags were used the size could still be excessive but pass the four line restriction. No more.
Now if a sig is too long it will be placed into a scroll box, like the following:
If your sig is large enough that it's now displayed inside a scroll box then you're strongly recommended to edit the length to fit the four line limit.
Additionally, signatures are now only displayed once per thread.