Well "Growth" was easy enough, we have a ton of specific tags related to various forms and states of expansion, and it's super befitting the website as a whole. But that would still have left a really large "Transformation" group, along with a bunch of odds and ends I didn't know what to do with, like Lactation, Pregnancy, Hermaphrodites, etc. I tried to draw a line between "Physical Modification", where a person is just changed in one way (pregnancy, lactation, change of age, change of gender, twins, etc), and full "Transformation" where the result may be indistinguishable ("You are now a Vase, have fun with that."). Looking at it again I'm pretty sure I failed, although maybe moving around some tags could salvage it?
Possibly move Bizarre, Conjoinment, FTP, Multibreast, Multilimb, and (Race Change?) to Transformation?
Hmm... I'll think more on it.
As for the difference between Animal Girls and Anthropomorphic, I would be inclined to agree with you that there's no real concise line to draw between them, and I was about to write as much... but then I realized that there in fact, is.
When we're talking about "Cat Girls", "Cow Girls" and other similarly 'lightly-touched' animal girls, what exactly are we talking about? As far as I see it, we're usually referring to human girls whom have taken on the various aesthetic and romantic traits of animals. Ears and Tail, occasionally horns, sometimes Eyes, Fangs, Hooves, or Claws. Commonly with romantic traits, such as increased strength, agility, flexibility, or 'mannerisms'.
Even at the extreme end of this, you only get partial fur coverage at-most, and only the extremities of the hands and feet are changed in structural form (if at all). An example of this would be Felicia from Darkstalkers. Animal Traits on a human base.
"Anthropomorphic" however usually goes far harder. Full coverage of fur or scales is a must, and usually it goes significantly farther, altering the facial structure of the skull so that the face is no longer distinctly human. The result is always a more thorough blending that's intended to evoke Anthropomorphism rather than rely on it. A human-like animal, if you will, rather than an animal-like human.
I stumbled upon this train of thought as I realized that the dividing line between these two things could be summarized as the presence of fur/scales and development of the face and torso. So maybe the tags could be "Animal Traits"/"Animal-Like Traits" and "Anthropomorphic", or something along those lines?
"Nipple Expansion", honestly I've hardly ever seen it. Usually it's along with Breast Expansion, or it's so extreme that I'd say it'd probably more fittingly rolled into "Bizarre Body Modification". But then, whatever?
Maybe change "Multilimb" to "Multi" or "mlimb"?
Hm... well, the goal with tags is to be as descriptive as possible while keeping a narrow focus. My intention for "Status Change" is to cover changes in social status as perceived by oneself and/or others. Generic, as opposed to the specificity born from the similar "Identity Change" tag. Identity Change covers Sharon becoming another person, Status Change covers Sharon becoming another version of herself. Cheerleader Sharon, Nerd Sharon, Maid Sharon, Stripper Sharon, Princess Sharon, etc...
"Cliche" often carries a negative connotation, I'm not sure "Role" would properly convey the intention however... "Social Change" might be too broad and nondescript. Maybe combine them somehow? "Social Role Change", or "Social Status Change"? Either way the tag could just be Role?
Edit: Also, I would recommend trying to organize the tags by name rather than abbreviation. Abbreviations can sometimes put things where you wouldn't expect.