Is http://lo.yodeya.com/ still connected to judaism.se? If yes, why is it not used?
The "yodeya" brand is currently an unofficial alternative name/URL for Judaism.SE. I own the yodeya.com and miyodeya.com domains and point mi.yodeya.com, yodeya.com, and miyodeya.com to Judaism.SE. I also control the blog that lo.yodeya.com points to. So, technically speaking, there's no reason we couldn't use it.
On the other hand, if we had something to blog about, it would probably make more sense to get an official blogoverflow.com blog and take advantage of the built-in tie-ins with our site and the rest of the SE network. So far, though, no one has volunteered to do any sort of regular blogging, which is what would be necessary to make it worth setting up a blog. We've had some ideas for regular content that could go in a blog, but like I said, no volunteers.
If someone wants to take up one of these ideas (or something else) and start writing weekly, we could request to have a blog set up. The best way to demonstrate that you're willing and able to do this is to just start doing it on meta.
Back to your quotation from chat, unless we have a blog that's fully integrated into the site, meta remains the best place to put site announcements. If we did site announcements on lo.yodeya, almost no one would know about them. In addition, the access controls and user identities for posting, responding, and editing here (or in an integrated blog) are all set, unlike with lo.yodeya, which exists on an unrelated platform (Blogger).