From this post it looks like the forum software does use Markdown, and other stuff, and HTML (but only safe HTML!). Looks pretty powerful. https://meta.discourse.org/t/post-format-reference-documentation/19197
There's also some formatting tools at the top of the text entry box - at least, that's what I see when using this on a laptop. (Not sure what it looks like on a phone or tablet!) That includes uploading an image (very useful!) so it's not limited to just Markdown.
Also – on my laptop – there's a live preview of how what you're typing is going to be rendered. So go ahead and try stuff!