Most yinglets can sit at a human table/chair of standard height (if you don't mind having only their heads visible to others/requiring them to pull their plate to the table's edge), but for easier access to the table's contents and ensuring visibility of the upper torso at yinglet sitting height, raising the seat by 6 inches or so will do a lot for their comfort. However (and this is an edit after considering the question a bit more thoroughly), I'm pretty sure if I went to someone's place and they went "oh hey Avi's here, here's some textbooks to sit on!" I'd go "...eh, no zhanks," and either stand on the chair or sit someplace else. I'd even keep a set of stackable risers at home and take 'em with me for situations like these to minimise awkwardness, even though any host in a world where yinglets existed would ideally have a set at the ready.
A previous version of this post had the yinglet example character casually conversing while sitting on a stack of textbooks, but lately one of the things that's been appealing to me most about yinglets as a species is -- hey, despite the small size, that's a whole-ass person in there, and they should be treated how they want to be! In my case, I'm short, impulsive, creaturelike, occasionally driven by weird instincts, and I might enjoy frequent headpats (though really, who doesn't?), but I deserve to get to sit at a comfortable height like anyone else, human or not. Pretty sure other yinglets would appreciate the thought, too.
(I've got other asks from months ago I've still gotta answer, but I was inspired here! Bonus scale ref after jump)

