Maybe it is more than an instance. Maybe it is an idea, a world-historical vanguard, light itself. 
actual attempt to answer (cringe)
We’ve been around for three years on a lemmy fork before federation. The lack of federation for years as well as the place we splintered off from (/r/chapotraphouse) already having a unique microculture within Reddit has given this instance, in my opinion, a distinct culture compared to general-purpose and even other hobbyist instances.
Regarding specifics, Hexbear is a vehemently queer-friendly/intersectional anti-sectarian socialist instance. Check us out 
Fully vegan? Nah sadly. Although our local vegan community is strong and outspoken. Also a significant amount of admins and devs are vegan. So there are clear rules about non vegans doing shit stirring. Granted, we’re not allowed to post vegan stuff outside of the vegan comm. Basically the non-vegans and vegans have well enforced rules of respect for each other. It’s not 100% ideal, but it’s the best I’ve seen in leftist, not explicitly vegan spaces. I’m thinking of a lot of those left Facebook spaces where admins would just post stuff like “well I’m just criticising white veganism”, all the while leaving space open for the whole community to bash veganism in the comments.
I like it here, and I think you’d like it here, but this place isn’t fully vegan.