Yeah this setting is messy in its current state. There’s no font size options for the post body text directly, but it does get affected by the “self text font” option (which should be separate imo).

That option isn’t there if you use any view type other than Cards or Slides though, so you have to change view type, then change the self text font, then change your view type back. This will change the font for the post body text.

Self text font is still missing the Line Spacing option which comment font options have, though

In the sidebar, hit the dropdown arrow next to ‘profile’. Or, go into your Profile and use the dropdown next to your account name

Yuuup. And some long-press options on pictures would be great also (save, share, share link etc)