i think i finally figured out (at least part of) why here and tumblr are so difficult to post on and why twitter worked so well for me.
i'm the sort of person who cannot form a complete thought in one shot anymore. it's an iterative process. i don't have the working memory available anymore to keep everything inside til it's ready, and drafting out text beyond two or three sentences like this is horrendously anxiety-inducing (probably due to a strong association with school, work, and other business matters that continue to make life difficult and miserable). this pre-dates twitter, it started shifting that way sometime in my teens. i've been a short-message chatter for nearly my entire online life.
even outside of the Culture (which is absolutely inscrutable to me, and that's a tangential subject) the way posting works here and tumblr, where it puts everything inline and quotes the entire previous post/thread, makes trying to communicate in the way my brain works range from stressful to impossible. i can't quickly "one more thing" without taking up a huge block of space and feeling like i'm being annoying.
even as i hover over the "post now" button i'm terrified that i'll think of something else to add that's too short to warrant a quote-and-add, and it'll take too long to hit me for an edit to feel appropriate.