We have no convention whatsoever. A good example: https://github.com/xtuple/xtuple/blob/master/lib/enyo-x/source/views/navigator.js#L58.

I'm happy to discuss what we might like to standardize around. `*Changed` is already enyo convention for an unrelated mechanism, so our starting point should be to not do that. Enyo's API suffixes their handlers with "Handler" for example: http://enyojs.com/docs/2.2.0/api/#enyo.UiComponent::handlers.
http://enyojs.com/docs/2.2.0/api/#enyo.UiComponent::dispatchEvent
I'd be happy to go that route.