Because there are actually three tani_* artists now and this isn't the first from pixiv, I just did an edit instead. It seems plausible that another tani from pixiv may be tagged in the future, and someone may try to name it tani_(pixiv), and get tani_(lupe) if we did an alias, and thus they'd be very confused. Or worse, think they found the right artist and we have two artists' work merged.
I know I've accepted _(artist) and _(pixiv) aliases before, but I try to avoid them if the tag count is low, and this was only 6 posts. The downside to move rather than an alias is it breaks subscriptions but there a trade-off both ways...
Which brings up the question of what my threshhold is... 10 ain't much more than six, so I guess I'll just do a move like above.
Although I moved to tamakorogashi as they go by on the webpage (たまころがし) and artist profile here.
I think I'll finally get around to asking albert for some kind of "subscription migration" functionality. That will make these borderline changes a lot simpler.