The point is to talk to your coworker first. You can’t know their relationship with their manager so you could do harm even if you intend to help.

Ok, an unintended consequences scenario?

I am interested though, when would praising a coworker negatively impact them via their manager?

This has already been clearly explained in the thread. If you care read it from the root.

The tl;dr is that you can’t know the relationship between a coworker and their manager. You may desire a world where that’s always productive but it’s simply not real.

If a manager is hostile to your coworker and you provide unsolicited feedback the manager could use your well intentioned feedback to sabotage that peer.

An example of this is “muulmen went out of their way to solve a launch blocker for my project.”

But do you know I’m not already behind on a failed project out of my control but helping in a way I believe best benefits the company? Your unsolicited feedback could be the final piece of evidence that gets me blamed for the delay and fired, even though I helped you and the company.

Do. Not. Talk. To. The. Authorities.

Speak for yourself. NEVER for anyone else.