That could be a useful feature. It's got vibes from the 90s, when there were a lot of different browsers and some of them allowed users to annotate pages and links [1]. I'm sure that there are a number of extensions to do that and still it's OK to have it in the browser by default.

[1] https://scholarlykitchen.sspnet.org/2013/04/30/iannotate-wha...