Curious: what made it annoying and rarely useful? We'd like to avoid the same mistakes if possible.
It's a terrible precedent and lacks any sort of standard :-/ I'm not a fan of this sort of pattern spreading.
At that time, the size/parse time will have much greater impact because the total size of libraries will be smaller or unaffected.
At the same time it encourages libraries to put significant error messages in their code without fear of bloat which helps your customers in the end.
Personally, I hope everyone will follow.
If Sentry or others that understand this problem space better create a standard format, we would be happy to switch to that.
Everything have to start somewhere. :)
Edit: here's someone complaining about it: https://github.com/angular/angular.js/issues/6077