A good number of strips will be pre-cropped, or the equivalent. So what you'd really want when the signature's missing is to have the poster do reverse-image as necessary so as to identify the creator, making sure to include that information.
There's also the fact that doubtless there will be posters ignoring such a rule / guideline, ideally necessitating mod intervention. Meanwhile, the one and only mod looks like they haven't been active in a month.
¯\\_(ツ)_/¯
