My projects (or contexts) are showing up twice!

Projects and contexts are case-sensitive.

Why are projects and contexts case sensitive?

Projects and contexts, as shown in the filter list and the pickers in the task text editor, show up exactly as you typed them. If your typed them with inconsistent capitalization, no attempt is made to harmonize the capitalization into one canonical version. If you wish to, you can use filters to identify the projects and contexts with capitalization you don’t like, and then edit those tasks to make the capitalization consistent. Also, you may use the project and context pickers in the task text editor to apply consistent capitalization to your projects and contexts.