Am I right in thinking the vast majority of this artist's posts should be tagged either hot or cold, depending on what the characters are saying?

Tag what you see, but I don't think only saying hot or cold is enough for those tags.

Insanity_Demon said:

Well, if it isn't then someone else can go ahead and remove the tags from all the posts I've put them on.

For future reference, you can do them yourself.

Since there's no real indication beyond the character just saying it, I don't think it should be tagged. Anyone in the future who might need to see all posts where characters say it's hot or cold could easily search on the Notes and get that information.