Hey! I read your little read more thing about Tim as being portrayed feminine within the fandom (totally agree, loved it). Though I have to say, I always thought that it stemmed from him being drawn as the shortest (with the exception of Damian because of Damian's age, and even then, I often see older!Damian portrayed as taller than Tim). It's like, for some reason, short = submissive. Is that weird or what are your thoughts on that?
I didn't touch on that, but yeah I've had the same exact thought process. It's not weird at all because I'm pretty sure that's a common social perception. It might have to do with the fact on average women are shorter or just the fact of size and power dynamics, ie the bigger stronger one having more control/ability to dominate. But I feel like that does play a large role on how easily he is feminized.
Comparatively he's always been shown as shorter than the other boys (again save Damian like you mentioned but he doesn't really count in this situation cause of age) in canon, but also he's usually drawn a slimmer build do. (Again taking aside the weird hyper masculinization some artist have done showing him with muscles the size of melons cause that doesn't really count.) One has to take in account though, when looking at scans you're comparing a boy ranging the ages of 12ish-17 to a fully grown man in his mid twenties and, well let's just go early twenties for Jay cause that's all over the place.
It's probably a combination of the female association with height and the power dynamic alone of just large males being more powerful, as both pretty much play on each other as reinforces of the same concept. Basically that being smaller/shorter means you're weaker and can't defend yourself as well.