[QUESTION] Have to have all the blocks the same styles by definition

First of all, your example/problem has nothing to do with the custom render in blocks (you'd use it to customize the UI of blocks not components in the canvas).

A solution is to set that class private

@artf Thanks for the reply! Sorry, because the example wasn't clear. It happens on every case, I mean, even when they are defined in the default template, and not only when a new selector is added. So, using selector:add wont fix all the cases.

Do you have any other suggestion? Thanks!

It happens on every case, I mean, even when they are defined in the default template, and not only when a new selector is added. So, using selector:add wont fix all the cases.

selector:add is triggered even when a new class is added from parsing. So, place it as a plugin, so it will be attached before the template is loaded and any new class will be passed by the listener