I agree with Ormus, but I guess the main question is - When we pay for our subscription to C3, are we paying to be able to use the software, or are we paying for support? Or both?
Even if you're not subscribed to C3, I know Scirra will still check any bug report from anyone, which is great!
Once you sub to C3, do you get more perks in terms of support?...not really, no, because anyone, free or subbed, gets the same level of support.
With other companies, when you pay for support, they have ticketing systems that staff and customers can both use, so you could email-in a bug a report, or pop it on the forum, and a staff/mod/volunteer would submit a ticket for you (because you're paying for this support) and they'll communicate back and forth until you feel happy it's resolved. OR you could submit a formal ticket yourself. If I could choose, I'd post bugs to the forum - I like the discussion that can come with it, and I like staying in 1 website.
With C3, you MUST submit it to Github (Unless there was a lot of noise on the forum post with other users complaining, then that'll attract immediate action). But that's absolutely fair, if we are not paying for support, which I don't think we are.
Time is money, especially when we are paying subscription fees. Noone wants to be bug-reporting for a subscription-based software, everyone would much rather be USING C3 to make their games and such.