On other blog platforms I use, clicking on a category or tag brings up all the posts within that blog which have that category/tag. In WordPress, apparently, clicking such a link brings up posts from other people’s blogs, instead. Not very useful when I want to direct potential readers to all the posts on a certain topic. Am I not using these correctly?
The links in your posts will always do this. Use the categories and tags widgets in your sidebar to link to those sections of your blog. This is also possible with custom menus if your theme supports it.