Human–machine stronger than machine? It seems to be pretty well established since the days of (the second) Deep Blue vs. Kasparov match that top machines can beat top humans at playing chess.

However, Kasparov seems to claim that the best combination is human+machine, assuming the right decision-making process.

I'm wondering if there's any evidence to back up this claim that a human+machine combination would be stronger than a machine on its own, or in other words, whether human reasoning can contribute something valuable to playing chess beyond what the top machines are capable of?

For example, have there been matches along these lines (human+computer vs. computer) that might shed light on this claim/question?
Yes. I remembered seeing a Reddit post on this, so I looked it up;
From /u/MortalSisyphus on Reddit:

At the end of the day engines win and lose games against each other. Which means their analysis is &quot;flawed&quot; in the sense they don't have an infinite horizon. It says 0.27, but if the move ends up with an eventual loss then the analysis of that move wasn't actually 0.27, it was -100.
Of course it is more complicated than that since each move contributes slightly, but the point is the same. The engine does blunder, just not in the way humans typically blunder. The blunders are basically impossible to see even for a 3000+ engine, but if the move(s) lead to a loss it is a blunder.
It is possible that a human seeing 3 roughly equally assessed lines could use intuition to pick the one least likely to be a long-term blunder, meaning a strategic mistake.
And of course humans have highly advanced opening theory, which is probably where most human advantage comes from if the engines in question don't have a very strong book.

If you want to see some human-machine chess, look up some modern ICCF games - ICCF correspondence games are played with engine assistance.