Wow...I knew I shouldn't have tried to help by clarifying that "platform" mistake. Some folks on this board make posting as fraught as boards on politics, religion, or oil changes.
Other than that, I simply replied to your subjective post "Why not just buy a used i3; one with much higher content and trim than the Mini would seem to have", which indicates you have no experience with a current Mini, with my own opinion based on experience with all three vehicles in question. Again, so much for trying to help the OP. And I have no idea why what I may or may not think of as "sporty" has anything to do with the post you quoted.
As far as "my money, my car, my decision" go I obviously chose a Bolt as it best fits my needs. I shopped the i3 but they don't work for me for much the same reason the Mini SE does not. If electric range was higher I would choose either BMW product. As I said before they are both just nicer places to spend time, subjectively of course.
Bolt vs Mini examples? The seat construction & materials and the dash/trim/other interior bits really make the Bolt pale in comparison. The narrow Bolt seats & the hard armrests can make comfort a challenge whereas the Mini is available with those fantastic BMW sport seats. That's an opinion btw.