It is about the sixth time i change the tag "rain" from Character type back to General type, having each time to browse through the 70 existing pics with this tag to find the very one that contains a character named Rain (usually Rain Silves) to edit it properly.

It does seem like some people are totally clueless about the tag searching feature and/or don't double check their tagging.
Assuming that i don't own a special browser, the picture's page DOES reload after editing tags, and it is easy to check for the tag count that would indicate the tag whose type was just changed ALREADY existed before the edit, and has a fair chance of having had a different, more relevant type.

"rain" is just an example, but i changed dozens of tags type over the last weeks.
Things like "wolf" changed into an artist or into a character tag make me doubt the one who edited this very tag has a clue about what he is doing....

Additionnally, changing a tag type during a picture upload, even after having checked it, is The evil, because of this : forum #1858
That is, unless you previously searched the tag in the alias list.

'Tear' seems to be a character tag now, and 'Poop' is an artist tag for some reason.

I think that's what you mean.

Those are easy to fix.

http://e621.net/post/index?tags=tan
140 pictures to browse in order to find those who need to be tagged tan_(artist)

Just do this:
If it's a character put "xxxx_(character)" and make that whole thing a character tag. Or "xxxx_(artist)" and make that an artist tag. That solves that problem....

That's not the issue at hand. The problem is people who are uploading the images aren't bothering to tag them that way in the first place.

Another example I've seen from time to time is the tag "freckles", which is also the name of an artist.

I had that problem a while back. I noticed that Felicia from Darkstalkers had to share a tag with all of the other garbage named felica. I had to manually go through the posts and retag ones of her with Felicia_(darkstalkers).