BUR #56022 has been rejected.
deprecate vertical_comic
deprecate horizontal_comic
It's been about seven years (forum #159659) since these tags have hit the scene. Their brethren in square comic has long since passed away, in favor of square 4koma (which later gave us rectangular 6koma). In that time, things have changed in the comic space which has made the tags unfit for use.
First, starting with vertical comic. I think it's always been somewhat of a farce of a tag, since it is the general format you would see for *koma comics. If it were properly tagged, it would be massive, and no one would be using it since a comic being vertical by itself says nothing. It's only once it is in relation to something else that it makes more sense. Some folks have used this tag to mean tall_image comic or similar, some use it as a sub-in for when you go beyond 6koma (speaking of, someone brought 7koma back - we may as well update it to be "7+koma", because going beyond 6koma is excessive, principally), and, most importantly for me, some folks are using it to tag webtoons.
It would make sense to deprecate it and just segment these individual aspects between the respective tags, particularly for webtoons, though we'd have to call that tag vertical scroll comic or similar because, looking at the tag history for webtoon, calling it webtoon would cause mistags.
On horizontal comic, meanwhile, some of the posts currently tagged feel like they belong in sequential instead, or whose horizontalness feels negligible compared to its contents, like the instant loss comics or the 好感度変化過程 KanColle comics. If we wanted to tag horizontality, just like with verticality, it needs to be in relation to something. If we want to have a tag that's, say, for stuff formatted like Western newspaper strips, we should have that rather than delegating it to an ambiguous tag like this.