It seems more often than not "slightly_chubby" is used in place of "overweight", "obese", and hyper "x" body part.

Aka, this is tagged slightly_chubby (it's hyper)
https://e621.net/post/show/1968982/anthro-balls-big_balls-big_butt-big_penis-butt-deo

This is tagged slightly_chubby (it's overweight/obese)
https://e621.net/post/show/1967127/big_breasts-big_butt-breasts-butt-domestic_cat-duo

This is tagged slightly_overweight (seems about right)
https://e621.net/post/show/1968534/5_fingers-ahoge-anthro-blue_eyes-blue_hair-blue_sk

As is this (seems about right)
https://e621.net/post/show/1967740/2019-3_toes-anal-anal_penetration-anthro-anthro_on

Just looking at the tag search, I'd hate to throw it all on a blacklist, as I like seeing realistic body types, but about half of it is tagged as "slightly_chubby" only, with no other indicator that some are obese/hyper.
https://e621.net/post/index/6/slightly_chubby#

Should I be changing these as I see them? It seems like other people have different standards for "slightly_overweight", as when I've retagged these previously they've occasionally gotten reverted.

I suppose the Tl Dr problem I have is that people don't like to use the tags "overweight" and "obese". Maybe people don't like the negative connotations.

It seems like other people have different standards for "slightly_overweight", as when I've retagged these previously they've occasionally gotten reverted.

Whichever standard most closely matches the wiki is correct (although a bad actor can technically shift the tiers around since the page isn't edit-locked, but besides that.)
If you notice somebody who consistently ignores the standard, it seems you can use that as a basis to report them, based on the fact that there are records getting onto people for consistently mistagging things like muscle size.

chubby is aliased to slightly_chubby and people tag chubby for anything from a little bit of flab to hyper. slightly_chubby is absolutely packed with mistags as a result.

janonymous1515 said:
people don't like to use the tags "overweight" and "obese". Maybe people don't like the negative connotations.

Ironically, in my experience the people who are into overweight/obese art are the ones who will tag such as simply chubby/slightly chubby, because they're unsatisfied with the lower-end of overweight classification.
You'll see similar with breast sizes if you go through comments on huge breasts/hyper breasts posts. In fact it's often the same individuals.

Do all the overweight tags (chubby overweight obese etc) implicate overweight? I'd like to make sure I'm not missing pictures when I'm looking for fat characters.

Thirtyeight said:
Do all the overweight tags (chubby overweight obese etc) implicate overweight? I'd like to make sure I'm not missing pictures when I'm looking for fat characters.

Everything above overweight implies overweight, but nothing implies or is implied by slightly_chubby.

hsauq said:
I always felt that it was being done unintentionally because in real life porn, I've seen chubby used interchangeably with fat, BBW, and sometimes even SSBBW.

This real life porn you mentioned was straight-up wrong, then. "Chubby" specifically means having a little bit of extra padding, but not having SO much fat on you as to qualify for "overweight."

Blind_Guardian said:
chubby is aliased to slightly_chubby and people tag chubby for anything from a little bit of flab to hyper. slightly_chubby is absolutely packed with mistags as a result.

Undoing this seems like the fix to make.

janonymous1515 said:
Undoing this seems like the fix to make.

How is that going to stop people from tagging overweight/obese characters as just chubby?

MagnusEffect said:
How is that going to stop people from tagging overweight/obese characters as just chubby?

It wouldn't, but it might help fix slightly_chubby