oh gosh. uh, it’s hard to start - I guess he’s difficult to pin down for a lot of people because we don’t - canonically - know that much about him? granted we don’t know that much about any of them, but what we do know about Feuilly is harder to package into a personality, if that makes sense.
We know he’s passionate about education and history and politics, especially foreign politics - that he’s a bit awkward sometimes and very intense when expression these. He taught himself to read and write - that’s dedication. He designed the barricade and ‘commanded’ his own team of sharpshooters at the barricade. We know he’s incredibly generous, and very earnest and hopeful. I’m not going to list all the thing we know about him from canon, because these are easy enough to find.
I guess I like thinking about how his past and his upbringing influenced him and shaped him; about how he became that person who, despite having no chances at education, spends his time reading and teaching himself all sorts of things. because you have a guy who very likely went through so pretty bad stuff - if not outright terrible, then just lowkey not great, you know? it depends on what you imagine. but still, despite all that, he adopts everyone as his family. he’s, as I said before, incredibly generous and passionate and earnest and enthusiastic. That’s pretty amazing. Even Enjolras admires that about him. He could have so easily become jaded and just gone on with his life trying to survive, but he didn’t. he gave everything he had, even though he didn’t have much at all, to make a better life for everyone - not just the people of France, but everyone in the world. Just. Incredible.
Also what the fact that he’s a worker and not a student means in relation to the other amis; but why does he join a group of students instead of a group of workers? he’s probably pretty young - in the 1830s, there was no law yet saying kids couldn’t worked. he probably started working around in a workshop or factory at around 12 or 13; even earlier. I read once a fic that explained he didn’t fit in in workers’ group because these people were fighting for their families, but their kids - he didn’t have any, they weren’t fighting for the same thing. Feuilly was probably alone a lot - whether that bothered him or not is also up for interpretation - until he found the amis, that’s it. :)