Do I actually need a separate sign-in for the blog and the forum? How do I sign into the forum? This sounds like way too much work 
Evidently you already have a forum login.
The forum is tied to you having a Beeminder account, so should be pretty smooth.
The blog, sadly, still uses Disqus for comments, which is a separate login. We have occasional ambitions to somehow integrate it with Discourse (the forum software) instead.
Feel free to start a thread on here about any particular blog post, that’s been done before with some success.