I originally wasn't going to engage in the 'blame game'... But I also plan to be racing on this track (with this group) in the future, so this could also be used as a good opportunity to learn from more experienced racers.
This is what it looks like to me as the 'driver' of the 924: This happened between 6 and 7, a stretch of track between two lefthanders that has a gentile curve to the right. It looks to me like the Miata exited 6 tight and off-line, and seemed to be inviting the pass regardless of whether that was their intent. The (5cyl Audi powered) 924 took what looked to be an ample (and intentional?) opening. Unexpectedly to the 924 driver, the Miata tried to return to the line after the 924 was mostly past.
Could they really have been caught that off-guard by the road curving? It's not like the pavement 'disappears' there by narrowing, it just curves the way roads do. So it should have been possible for the Miata to hold lateral position, unless this was literally their first time on this track and got mentally lost or were spending too much time worrying about what is behind them and too little about what is in front of them. Perhaps they could have (poorly) chosen to changed their mind to go back to being on-line after first opening up the line for passing, or potentially even (intentionally or not) just run a 'blocking' line through there without watching their mirrors? Short of their mirrors having just fallen completely out of adjustment and the Miata being about to head to the pits to fix them, I'm not sure how they wouldn't have been aware of the 924's presence and inevitable passing to plan for. Another driver also noted a run-in with this particular Miata as having dangerously taken up much more track than necessary when being overtaken by significantly faster cars. Regardless, I'm struggling to come up with any explanation that isn't either a dumb or dick move on their part.
Meanwhile, I feel the 924 had been patient and in the Miata mirrors for multiple turns. They had zero reason to believe the Miata didn't see their presence nor passing. If anything, they had reason to believe the Miata was letting them by. I understand that people make mistakes, but short of only passing on the front 'straight', I'm not sure how much bigger of an opening there needs to be for the 924 to not be engaging in 'asshattery' there... I genuinely want to know, because even trying to be a 'safe racer' I can't say I would have done differently, and I don't want to find myself in that situation.
If you were the 924 driver, what would you have done and why?
If you were the 924 driver, what would you have expected the Miata to do and why?
If you were the Miata driver, what would you have done and why?
If you were the Miata driver, what would you expect the 924 driver to do and why?
As a visual aid, here is a track map with racing line and driving school designated passing zones... Note that this specifically happened in one of them.