I'm not sure what conversation you're participating in, but the parent comment was flippantly discussing the possibility of taxes so draconain that the GIDI coefficient would approach zero:

"The wealthy kind of are an endless source of loot because the definition of wealthy is one relative to a median, so you'll either end up with everyone roughly equal in wealth (is that a bad thing?) "

In the world advocated for in that comment, with aggressively averaged out income/wealth, there is no incentive to produce value above what is required to reach the average income.

It's a Rawlsian question of "how can we structure incentives such that everybody is better off?"

Now, the metric for "everybody is better off" is still an open problem, but there seem to be near pareto optimal steps we can take, like a high threshold wealth tax.