I just want to clarify here -- are you aware that personal wikis and server software such as MediaWiki are different classes of software? [...] Personal wiki software is generally just an ordinary program, meaning it has it's own GUI and can have features that it would be insecure to expose over the internet.

Apparently not! I didn't realize "personal wikis" referred to wikis implemented as separate, ordinary programs; I'd thought they ran on web-server-plus-scripting-language stacks as MediaWiki does, just with smaller, simpler codebases and far simpler database schemas (or indeed a bunch of flat files instead of a full-blown database).

Anyway I mainly commented because using MediaWiki only for your own personal notes seems rather like cracking a walnut with a sledgehammer.

Yeah. Were I to do this again I'd look more deeply at the simpler personal wiki programs out there rather than just shrugging and going with the more familiar choice.