Haha, yeah - I absolutely have strong feelings about Posts with title as well. 
I also have some compulsive traits, so I know that that makes it worse. But I still just don’t completely buy the notion of “The limit could’ve been whatever, and people still would’ve struggled”. A limit of 100 is different to a limit of 300 which is different to a limit of 500, etc.
And I do agree that there should be a limit, and that a bunch of long posts on the timeline is a bit messy (even though I think read more buttons fix that pretty easily). I just think 300 is unnecessarily frustrating.
I like the idea of micro posts being a thing and, as I mentioned, mostly be “one idea”. And if I were to pick a limit that feels like a sweet spot to me, I’d go for something like 6-800. Even though not all, or even most, of micro post would go towards that limit, it would remove my frustration at least. But as some might find the occational 700 character post offensive to the senses, I wouldn’t mind going with 500 - with the interoperability gains that entails.
(I know this is a losing battle - but I still feel the need to say that I find this really, really frustrating.)