Is there more backstory to this whole Reimu protecting a plant from a derpy looking Marisa? I think there's 2 of these now

2ch:
たくさんあったから！おなかすいてたし！
それにお花さんが！お花さんがお食べなさいって！だからまりさは悪くないんだぜ！

There were so many! And I was hungry too!
And the flower! The flower told me to eat it! So it's not Marisa's fault!

Has there been an artist tag for all of these little comics?

Nope. Although this kinda looks like unknown_14 to me