My single greatest complaint is the same as many other people's single greatest complaint: column widths.
This hits me two different ways: while mobile, and when reading bigpage/printable.
On mobile, it seems not to set the text, always, as reflowable.
When reading the bigpage, something on the page makes the column a fixed width which is too wide for my 12" monitor, when I use ZoomTextOnly to increase the text size far enough for my aging eyes, pushing the edges of paragraphs off the screen. If I don't use printable, it's worse.
I know that article text, or at least comment text, is -- at some level -- reflowable, as it *isn't* if you use plaintext instead of HTML to enter a comment...