When writing posts, the formatting is different. When you write a post, there should be a number of options in the text box above it. One of them looks like a chain. If you highlight a block of text, and click that button, that's how you do hyperlinks. The other things should be pretty self explanatory. It's all in that toolbar though, nothing is formatted as it is in comments.

In the mean time, you can edit the post and repost it to your drafts if you'd like.