[ralfhn]

You don't need an extension if you're using chrome. You can override the css using devtools and persist the changes locally: https://egghead.io/lessons/chrome-persist-live-style-changes...

[spion]

I do that but I'm tired of chasing down the variety of places which cascade to the main text.

With a little bit of search, looks like the reader mode extension does what I want (in fewer step)