Check out: The Definitive Guide to HTML Headings for SEO (H1-H2-H3-H4-H5-H6)
I think this is why other forums like Wordpress.org disable usage of headers. I run a technical forum with Discourse where symbols like # and - are used a lot and thus results in undesired header formats.
QUOTE : ‘ We do use H tags to understand the structure of the text on a page better, John Mueller, Google
QUOTE : “ Google looks at a lot of different things … even things that are like really highlighted like h1 tags and stuff like that.” Matt Cutts, Google