I've actually been thinking about this recently too. As well as there being a lot more threads than micbroblogs, since voting tends be less important on microblogging platforms, the number of comments on a post is often the determining factor when sorting by hot, top, etc so the microblogs get drowned out by the threads with votes.
I think weighting microblogs will be a little complicated since many microblogs have 0 score and 0 comments so giving them a say 1.5 multiplier won't change the sorting result. Additionally mbin currently has an open PR for combining the thread/microblog timeline server-side which we'll probably switch to using since it reduces app complexity. So it might be worthwhile bringing this up there too. In the meantime I'll try experimenting with how to give microblogs a bit of a boost.