If someone of their own choosing puts money into it, for example to purchase colors or a hero mech or even one of those fabled founders packages from a while back, that doesn't change the fact that it's a free to play game. You're not paying a subscription fee, you're not paying for play time. You *might* be able to make an argument that you want your premium time back or at least the ability to pause it when you're unable to play but even that is kind of sketchy.
When someone puts money into the game I can understand they might get upset that it has an issue which makes it unplayable for them. The issue with thinking you have a right to complain comes in when you honestly believe that. You put money up for a product knowing that it's not fully developed yet. You know full well that there are issues being worked on and that in the process of adding features or solving current issues more might pop up. If you then decide to pay money anyways, it's on you. PGI didn't force you to pay, PGI didn't tell you that you have to pay to be a tester of their unfinished product. You, having faith in the company and believing in the benefits of the product decided that you wanted to put forth some money for the possibility of enhancing your experience.
In fact, I would highly recommend everyone read the Terms of Use agreement and the Code of Conduct.
http://mwomercs.com/terms http://mwomercs.com/conduct If you don't like clicking on links in peoples posts, both are also available on the bottom of the page.
All that being said, I too have spent money on this game. I too get upset when I encounter bugs or other issues. I do know though that I don't have a right to complain. If someone wants to complain that's on them, but it's not a right. It also doesn't do any good to help solve any of the problems they are having, while actually reporting bugs in the correct manner would help.