If the artist puts their signature leave it, it was meant to be there just like anyone who signs traditional art. If they didn’t sign it, that’s ok because that’s how they wanted their work to be.

In either case it is always good to link back to the artist/author’s website where the comic can be found, or social media post in some cases. Not only does it help by driving traffic to that artist/author, but also sometimes they include bonus panels, or alt-text that gets missed when posted here.