What, we're talking about wikis and vim, and not mentioning vimwiki?

https://github.com/vimwiki/vimwiki

I tried a whole bunch of personal wikis over the years (I see Zim has been mentioned, that's one of the ones I remember trying) and this is the only one that stuck.

The github page shows some basic markdown, but it also handles nested checklists (parent nodes can be partially checked off) and understands tables (automatically fixing spacing so columns stay aligned). It can also render to HTML (though I don't use that feature) and has a whole bunch of other stuff too.