It does actually, as successful gamblers are more likely to hang around. Most I know don't post on this forum, but I can also guarantee that they would not be supporting martingale.
Also, if martingale was so successful, many of these pro-martingale gamblers would be coming back to throw their successes in the face of those who advised against it. Sure, some may not be bothered once they're living the high life, but at least one of them would be back here to cause a storm.
Depends on the forum and the person. Some will generally lurk and have low post counts, while others will get into discussion and have high post counts. The easiest way to tell a sharp bettor by the terms they use and the concepts they understand.
This means nothing not because of your credibility (and I never suggested post count creates credibility), but because the sample size is too small. It takes thousands of bets for a proper sample size.
As to why you aren't credible, it's because you're not knowledgeable. You have no idea of sample size, don't understand why martingale won't work, overbet, and have made no mention of how your bets are +ev. Like I said before, the terms someone uses and the concepts they understand says everything about their level of skill, and unfortunately this all suggests that you don't have any, and that you're just a regular gambler. Feel free to prove me wrong, but you'll need to provide mathematical proof to do it. I can save you time by stating that the maths isn't on your side, but I doubt you will believe me. I'm sure you're convinced that your system works as it seems logical in your mind and has worked for you so far.
It may seem I'm being rude and blunt and it's likely you'll dismiss me as being an arrogant fool who doesn't know what he's talking about, but the true fool is someone who doesn't even consider advice. There's no harm in considering my advice, even if you don't think it has merit. I suggest you read the previous martingale threads here and also do your own research, and if you're still satisfied that your strategy will work, go ahead. If it will work as good as you think then taking the time to prove so won't really hurt, unless of course you're afraid to do a little work.