So I just sorted out a list of almost every tail tags for myself.
Here are my questions:

1. Rename tail_coil to tail_coiling?

just popped out recently (while I am editing wiki) for distinguish between coiling.

My thoughts:
I think this tag can stay. But I would like it to be renamed to tail_coiling, to keep it consistent with coiling. I am not sure if it should also implies coiling.

2. Is coiled_tail still needed for tagging?

I see there is a lot problems between this and tail_wraps. Then I just noticed that these tags can cover that part pretty well:
tail_around_leg / tail_around_waist / tail_scarf / entwined_tails

They are more intuitive than coiled_tail / tail_curl / wrapped_tail or whatever I cleaned up, I think. If there is anything not covered, that would be just tail_around_arm and tail_around_object.

Example:
post #160626 post #854970

By the way, I think many of them should not be tagged prehensile_tail, because their tail are not trying to grab something around, or coil on something to balancing themself.

• See also: forum #97285 - \tail_wrap usage (Jan. 2014)
• See also: forum #151535 - Wraps (Feb. 2015)

3. The tag for bandage-like tail_wraps

Example:
post #386804

My thoughts:
Use tail_bandage instead. Correct me if bandage and wraps are not same, because I actually don't know the differences. I always call that bandage.

• See also: forum #188816 - Something needs to be DONE about tail_wrap (Mar. 2016)

4. hanging_by_tail and lifted_by_tail

They are messed up, we need a clear definition on wiki for them.

My definitions:
hanging_by_tail is using the tail's own force to suspend in the air. Commonly with prehensile_tail.
lifted_by_tail is to be suspended in the air by external force.

5. Usage of tail_play?

The range is ambiguous, so I want to suggest mine. I think tail_play should be used only when:

• The tail is rubbing the genitals, not penetration / tailjob / tail_suck / tail_lick.
• The tail is grabbed by hand and used as sex_toy.
• Stroking the tail like a penis or other weird actions.

Example:
post #834113 post #889310 post #187509

post #470376 <- This one I would tag head_tail + tail_around_leg + tail_play, no tail_sex.

• See also: forum #156628 - Tribadism, Frottage, Tail_Sex and Penetration tag issues (Apr. 2015)
• For reference: See the description of tailplay (That tag should be aliased)

6. tail_slap / tail_swipe / tail_whip

They are same kind of movements. I would like to know if there is a word that can cover them all? But they are all underused and may not so important anyway...

7. Why is tail_mouth a species tag?

Isn't this some kind of mistake? Or because they are so cute, so the tag's type doesn't matter? I mean, @Genjar already separated some specific species to tailmouth_(species). That's good job.

• See also: forum #192713 - miscategorized tag: Tail_mouth (May. 2016)

8. What are docked_tail and bobtail?

I am unfamiliar with this subject, so I need someone to write descriptions for their wiki. That will help a lot for tagging.

9. How to tag this tail?

post #77685
Should this membranous part at the end of tail be called
webbed_tail / tail_fan / tail_fin / tail_frill / tail_membrane or what?
I want to have a tag for them. I think tail_frill is the primary choice.

10. ridges / tail_ridge / ridged_tail and spines / tail_spines etc.

Pending.
I will talk about this subject in another topic. Because they are kind of complex, and probably never discussed before.

Notes:

If someone decides to clean mistagged tail_wraps tags, please don't forget to delete wraps too.

After this discussion is settled (I hope), I would like to start updating wiki and retagging these tail tags. Just let you know, I already cleaned up some inferior or misspelled tail tags. And some of the tags that still needed to be aliased or cleaned are listed on the tail wiki.