The general pessimism in the thread is because of bogus and impossible claims combined with unprofessional responses from the manufacturer himself. If you remove all of that from the start of the conversation what would have followed would have been a healthy dose of skepticism, but a lack of negativity.
I'm ambivalent. I'm neither optimistic nor pessimistic. I'm a skeptic, which is a healthy and good thing to be in all things. Please note that this is different than being a cynic. Skepticism good, cynicism bad
Don't sweat the English thing. You speak English as well, or better, than many native speakers.
"Known quantity" means that there's enough information on-hand to make a decision without needing to do more research. If you say "Hipshot versus no-name" then I'll pick the Hipshot because I know enough about them to be sure I'll get something workable, whereas "no-name" tells me next to nothing other than the fact that it happens to be a bridge. That said, Hipshot has a lot of variability in models, so I would prefer more information.