How to tag artists in multiple Groups?

Just encountered what may be a bug.

For http://danbooru.donmai.us/artist/show?name=kurenai_yuuji
the artist is a current member of futanarun and former member of FruitsJam.

However, I cannot put this info in using commas to separate, as it creates a new tag futanarun,_fruitsjam.

The group section doesn't work that way. You should make note of "being a former FruitsJam member" while keeping "Futarun" in the group section.