Absolutely not. It's got a bit of an edge without seeming like something an angry teenager came up with - murder.im or so, "Riot" doesn't have only inherently negative associations -, it's short, easy to remember... it would've been a great name for many software projects, but especially for collaborative, communicative software I find it to be a stellar choice.
I actually wrote a reply explaining why it was a great name and vector somehow fell flat before understanding that you were being genuine. I agree. Riot has that edge but a Riot is always a group activity. And it's something anyone can join. They only need jump into the riot.
> "Riot" doesn't have only inherently negative associations
???
Could you provide some, I can't think of any.
Also Vector seemed fairly decent (with the small plus of the matrix/vector association). Riot isn't much shorter then Vector, it has violent/negative association, and changing names (unless its a major improvement) seems like a bad idea for a piece of software relying on network effects and trying to become popular.
Riots often occur when groups feel they have no other recourse. There is sometimes a positive fallout from the riot but at such an extended time that it isn't clear the riot had anything to do with it. It's a group activity that shows a group of people all feel similarly about a subject. An expression of which is usually considered positive except for the presence of destruction and violence during a riot.