No, I think you misunderstand. If I'm arguing with you, my intent is (usually) not to convince you, personally. This is usually because I pick arguments with people I suspect are speaking in bad faith, or who are heavily emotionally invested in an idea. My intent is to convince lurkers.

You might also notice that as I get further down an argument thread, I tend to engage more directly with the person I'm arguing with. That's because there's less audience down here, and we're actually having at least a little bit of a productive conversation.

So is honest argumentation effective or isn’t it?

It can be effective but it is rarely efficient. In the time it takes you to present a detailed, sourced, and well-reasoned argument, and convince a single person who strongly felt the opposite way, twenty other people who have no strong feelings either way have been convinced by a well-timed quip or insult. And that's if you could convince the other person at all.