I've been on tumblr since 2011 so I'd like to think I know some etiquette stuff, but I'm so confused reading your story. I'm also not anywhere near any gifmaking circles because I don't really know how to make them these days, the way I learned how to make gifs like 15 years ago is not possible anymore as softwares have moved on (without me). so it might be that there are some etiquette things going on in those circles that I'm not aware of.

I think the only thing I would've done differently from what you did is drop the original gif creator an ask and say you want to use x gif in a post, with credit, and would that be cool? most people I think would say yes, go ahead. what other people then get up in arms about is *their* problem and the block button is free to use.

I made a gif maybe once and posted to tumblr where it then automatically entered the built-in tumblr gif tool system, which means that maybe once a year I get a random notification that somebody used my gif in a post via that built-in gif tool system. every time I'm like ??? what??? (because I always forget that I made that one gif once upon a time and then get confused that somebody wants to use it.) makes me wonder if the people who uploaded popular gifs get a lot of notifications about it... but also if any gifs one uploads to tumblr enters the built-in tool system then there is just no policing who then uses them, you know? and that method comment-jerk describes with all the html steps - literally never heard of it.