For the style of reading I normally do, this particular width is actively harmful to my reading comprehension. I would prefer just a bit wider text generally. This is something which the site does inflict on the reader. I agree that many sites are too wide in general, but this feels is too narrow by about 33% for my liking.

Additionally the way that the background degrades to a border around the text when using dark reader also causes problems in a similar way (due to the interaction between jagged text and a strong vertical line.

These are subtle points though, and I appreciate the many annoyances that are not there when reading Rachel's stuff.