One of my (nsfw) gif's got removed, probably because it looked to much like an original video.
My take would be that it was transformned enough to the point where you couldn't recognize the original face.
My question is to what level of transformation are we allowed to post content, because i doubt we are allowed to post original clips here (or ones with the denoiser set to 0,01)
I don't think there are issues with using gifs. I use them all the time.
What you need to take into account are Civitai's terms of service. More likely than not your gif was not in line with the ToS.
You don't describe the video so I can't say what it could be. If it was a real person, it could be the context (nsfw) of the animation; it could've looked underage; etc.