You might not like tipping. (Again: I don't.) The person you're rationalizing the stiffing of probably doesn't like having to work for tips. Capitalism kinda sucks and the person-to-person patching is something that more fortunate folks just plain get to do. Sorry.
You aren't saving the world by tipping--but you're not making it a worse place, and that's not nothing. Similarly, by not using a service that does its employees dirty without making it right, you are pressuring them--if, admittedly, mildly--towards decent behavior. That assumes that you make it very clear why you're doing it, and you totally should, because communication is part of ethical consumerism. (For similar reasons, when Amazon, Uber, etc. recruiters reach out to me, I underline the way they treat their workforce as a major reason as to my disinterest. It's a data point, and only one, but it's what I can do.)
If you were not informed, then there is no moral weight for not tipping either.
In a situation with 3 parties, there can be any number of immoral people from 0 to about 9 billion, so I don't know why you immediately assume that because the commenter is immoral that doesn't mean the company isn't also behaving immorally.
If the company wants to incentive good quality of service, they can do so explicitly with direct ratings instead of some unclear way of tips.
It’s immoral to shop somewhere that doesn’t pay proper wages. Employees should not be dependent on your charity because a company decides to save on its tax and wage bill.
Don’t reward companies that do this. Don’t promote a race to the bottom.