The article you linked mentions a litany of active lawsuits against UHC, many of which were already initiated prior to the murder of Brian Thompson. UHC was already on the legal chopping block prior to Luigi's actions; in fact it seems fairly obvious that the preexisting lawsuits and bad publicity were the reason he chose to target Thompson specifically.

Let's dig a bit deeper into the article. Right off the bat, I'd like to point out this tidbit, which perfectly supports the argument I was already making in this thread, namely that nothing has been changed by the murder.

Still, Potter warned that UnitedHealth Group’s own claims about reforms to its denials process should be treated with skepticism. “In my view, I think this is mostly for show,” he said. “It’s mostly for PR.”

As for the lawsuit in question, it was filed by some random shareholder from NY, who has no more access to the hard data than we do. He was concerned that

the company’s new projections for 2025, released in April, forecasted a significant cut in earnings.

And in an attempt to explain said concern, this talking head speculated

Wilkes, in an April media appearance, attributed the stock value drop to “probably United, and maybe the industry, pulling back on prior authorizations” — i.e., denying care to patients less often.

That's not any kind of proof or data, it's just speculation. Furthermore,

Shortly after the new investor case was filed, attorneys for CalPERS intervened in the new investor lawsuit, and last week, the plaintiff agreed to drop the suit and consolidate it with the larger case.

The lawsuit in question was promptly rolled into the comprehensive legal action which had already been initiated prior to the murder. And in case you didn't read the whole article, they also mention that

On Monday, shareholders greenlit a $60 million pay package for the company’s CEO and shot down a proposal that would have increased investor scrutiny of executive payouts.

Bottom line is, your characterization of the legal action as "UHC investors suing to increase the denial rate" is reductive and inaccurate, although to be fair to you, it simply mimics the editorialized perspective of the journalist who wrote the article. The parts of the article which emphasize that interpretation of the lawsuit are basically just the journalist pandering to the lowest common denominator which comprises the majority of their audience. In other words, the writer of the article intentionally sensationalized the nature of the lawsuit, which is really quite a boring legal footnote that doesn't make any of the claims implied by the article. I.e., it's clickbait, and it's obviously working.

I do appreciate you providing a relevant link that at least attempts to answer my request for evidence of the previous commenters' claim, but unfortunately it's not a very strong piece of evidence.

Lastly, I'd just like to point out that even if UHC does end up changing its practices and extending more coverage, all that ultimately means is that rival health insurance companies under less legal scrutiny will expand their market share proportionally and it'll simply be a situation of new boss, same as the old boss.