You could say that formatting tools should be evident, but it's clear that newcomers aren't aware of them in most cases, for example adding images to the post. Countless times I've edited post just to add an image.
What do you think about adding to the tour simple animations with brief demonstrations on how to use them? Just before the "Find a question to answer, or ask your own" section.
Considering that these are Q&A sites, and the new users are prone to jump directly to ask a question without reading the help section, but may at least take a glimpse in the tour.
The goal with be to reduce poor quality posts, make posts clearer and readable, without having to rely always on editors.
Just an idea. Of course another explanation is that they just don't care, nothing can be done about that.