Like many other mobile games of its ilk, Fire Emblem Heroes frequently releases seasonal and event characters in unique costumes, such as the recent Sophia (post #3818298). However, unlike those other games and characters, they are not given specific character tags. For example, azuma (soft voice of spring) (azur lane) or scathach skadi (fate/grand order) are different character tags from their "base" forms. With Skaði, she is a different character in lore, though I don't know Azuma. But osakabe-hime (swimsuit archer) (fate) is very much the same character. And I'm uncertain post count is a trigger, either, as tashkent (the bound cruiser) (azur lane) became a tag in about a dozen or less posts.

So, should those Fire Emblem characters be given alternate character tags, such as Camilla (Light of Nohr) for things like post #3597531 and post #3664708?

I was thinking of making something like that, but in the end it's not really needed as most FE characters rarely get artworks, with the exception of ones of recent games.

AL skins and Fate characters are an exception for the amount of artworks they get (and also them being different characters on Fate's case)

Even if, Granblue has many alt outfits for their characters like FEH, but only Gran and Djeeta get tags for alt outfits.