I never understood why TG TF is used to describe content that's just TG.

I always thought it was supposed to be for, like TG that's also Furry or something. the TF descriptor is kinda superflous in this case.

Base +7, ranoya +6, qrsWtuv +8, F-O-X +6, yht169 -6, Skiewolve +7, Eleclight +6

I think it's because nowadays "Transgender" on its own has a certain other context/implication that's way more common now. The TF is there to make it a bit clearer, maybe. I've seen people refer to it as "Gender Transformation" or just "Gender Bender/Change" now that TG/Transgender has been 'taken over'.

Base +6, qrsWtuv +8, Sukaira -6

If the act of transformation into the genderbent character is shown, I think it's valid to tag both. It's not restricted to transformation into another species, I believe.

Base +40, Celeadyne +8

I think Transformation is a legit label any time a character undergoes drastic physical changes to their body.

Transgender is a weird case as others have said. I believe technically it's supposed to refer to a gender transformation, however a lot of idiots lately have been using Transgender interchangeably with Transvestite. It's completely wrong, but there's nothing we can do about it. I think in some cases people even use "Transgender" to mean they are homosexual.

Gender Bender is a similar case. It's a more vague term that I often see applied to both Gender change and Transvestite stories.

It would be nice if e-hentai would do an overhaul of their crappy labeling system. There's a lot of room for improvement.

Base +3, Rule63MePlease +3

Gender bender is not necessary include transformation. Body swap, surgery, some characters such as Ranma (even if he/she has not transform in the particular story), an alternative reality, where known character has opposite sex - it's all gender bender.
Sometimes I wish we have more specific tags for different gender bender types. List of tags not always working, because it's often several stories in one gallery: one with gender bender, and another with transformation, but not both together. It's even may be a two different characters in one story: one is genderbent from the start and another transform into little black pig. And it again not what I looking for.
On the other hand, same thing can be said about other tags too. Each of us could list a lot of details that matter for his fetish, but not fully covered by tag system. And more complicated tag system would be hard to maintain. Even in current condition people are confused too often.

Base +6, Rule63MePlease +3

I'd say surgery qualifies as transformation so long as it's extreme enough. But yeah, there's plenty of TG/genderbending stuff not involving transformation, such as bodyswapping, bodysuits, possession, alternate realities and so on. One immediate example of this is the whole "Great Shift" scenario, which amounts to a mass bodyswap phenomenon basically and has given place to thousands of TG caps (mostly bad ones too, admittedly). In this case the character is transformed and so it qualifies as "transformation", even if it's into a human being of the opposite gender only.

Base +6

这定是极好的

Base +5