In the end, it wasn’t strictly my redirects at fault – I was just assuming I must have done something wrong because how could a DokuWiki plugin stuff things up as badly as this?!

Narrator: The DokuWiki plugin did, in fact, stuff things up as badly as this.

Note: I can’t see where I may have a mistake in the plugin configuration/setup to cause this incorrect setting, but that exploration is for another day.

I probably did muck up my redirects by trying to troubleshoot them – they’re back to a simpler, saner set and seem to be working. Huzzah!