Bugs. Lousy, yucky bugs.
Everything has to do with the fonts. The base font, in particular.
You can’t set it to ‘large’, else the system screws up.
The headings aren’t perfect either.
In small or normal text, the big letter starting the post is either above or below the line. Large headings are ugly.
So all you’ve got to work with is the default font if you want to see a tidy blog.
So Devs, lemme know when you’ve fixed it. I spent countless hours figuring this out.