So, I write an entry and leave it assigned to "Uncategorized" only. I then write a second entry and assign one or more custom-created categories to it. When reading the entries on the blog, the links for the categories behave in a manner I would not expect.
The links for the "Uncategorized" category point to myblog.wordpress.com/tag/Uncategorized, which is what I would expect. Yet any custom-created categories link to wordpress.com/tag/xxxxx. I've also tried creating my custom categories as children to "Uncategorized", yet arrive at the same results.
My category links should link to my own posts only. What if I routinely post in a "cooking" category, and a viewer of my blog wants to click that category to look at more of my cooking posts? They are suddenly presented with a screen of posts by everyone else, rather than only my posts. The links in the "Categories" widget point to my posts, I would expect and much prefer that those same links next to each of my posts would have the same effect.
I'm quite hoping that this is actually a bug and that the subdomain is simply being forgotten. To have this one set of links that takes a viewer away from the blog they're looking at is pretty counter-intuitive. I won't bother tagging my posts if they won't do what they should be doing. :(