Seems to work on #MissKey.> They can convey meaning well
If everyone agrees on the meaning of the picture, sure, but this is not the case. Various emojis can have vastly different meanings to different groups of people. If you're also going to add in custom emojis this is going to be even worse, you're throwing around emojis that are literally undefined by the majority of the world population.
With your example "boosts appreciated", making a hashtag BoostsAppreciated is clear, concise, and accessible to all. I've never even heard of a dedicated emoji for this, and if you suddenly started to use those I'd have to wonder what you're trying to convey, and use the alt-text to actually get anywhere. Seems like more hassle than just using text in the first place.> They can be used in addition to other textual hashtags
This is true, but do you expect people to just use double the hashtags going forward? One with readable text, the other in image form which you then have to hope works in every context?> textual hashtags [...] aren't always as accessible in their meaning either
Everyone can make "bad" hashtags, but I don't think making the pool worse is going to improve that. If any, it'd make it worse, now people can make bad hashtags with both text and images.> There are cultures around emoji use, that give meaning in certain contexts, and those cultures are part of social fabric and cohesion then
That sounds like a rather big assumption. Are you aware of any cultures that are currently unable to use hashtags, that have a strict need to use basically any image they can think of? To me this sounds incredibly unlikely, especially in the context of the #Fediverse.