Is there any difference between these two artist tags? If not, then they probably should get aliased.
I’d keep anonymous artist, since that already has a description and another alias.
“anonymous artist” is a special site tag similar to “artist not to be listed” which is used to mark artists who wish to not be identified: Use for tagging images where the artist wishes to remain unknown. Do not use together with “artist needed”, which implies that an artist should be tagged.
“artist:anonymous” is sometimes used by an artist who identifies themselves as “anon”, and “artist:anonymous” may also have the tag “artist needed”. So one is a very hard “don’t change this” classification, where the other often just means that someone on a *chan created the image.
