[zerocrates]

I also think this is a pretty reasonable change, since it already requires users to edit files, so about:config is not really a major additional step.

But I also would imagine the usage was quite low already and any incremental hassle will push it lower and it won't be hard to get to an analysis where maintaining a rarely-used non-default codepath is seen as not worth it. Of course it all depends on what's going on with the specific code at issue, but the basic point of my post is that "nobody is proposing to remove this capability" is true, until it isn't.

This isn't a feature I actually use, but I also find the removal of a minuscule startup delay of a program I don't actually start very often to be a pretty marginal improvement, so I don't really have skin in the game in either direction.

[plopz]

I use the feature, but only because an extension I used before, ClassicThemeRestorer, isn't supported in the new extension ecosystem. The only workaround is to use the css files. I would imagine a large percent of people that used to use the extension didn't migrate to the css files when extensions broke. So they wouldn't be counted in metrics. Also the experience is much worse for an end user since extensions auto update, but changes to the css files have to be manually updated.