@tournesol Je me souviens d'une image représentant un gars derrière un comptoir, avec un texte qui disait "Without ALT, best I can do is give you a Like".
The most common-but usually not the only-response, cited as a primary or secondary reason in about 75 replies- had to do with feeling unwelcome, being scolded, and getting lectured. Some people mentioned that they tried Mastodon during a rush of people out of Twitter and got what they perceived as a hostile response.