And your comment is another proof that people tend to assume everyone else is an idiot.

I think his comment was quite appropriate, and did not feel there was an implication that he thought anyone was dumb for not having known about the alternative approach to getting Reddit data.

Often times programmers and the managers that drive them are way too quick to get going building or solving something with brute force. If they would just be patient and stop for a moment. Spending even a mere 30 minutes extra doing your homework on a problem can save hours or days in dev time.

Saying that that was a proof of spending 15 minutes to search about Reddit API would save his time implied that kybernetyk didn't do that research.

But kybernetyk already said he did the research before and that Reddit's API is not good enough for his requirement.

So this is not the case that 15 minutes of research will save the time. And his comment meant he assumed kybernetyk didn't do research, i.e. being dumb for not doing search.

Let me tell you what I thought when I wrote it...

I did not assume that kybernetyk was dumb or anything, I simply chuckled and thought to myself ouch haven't I done similar mistake before?! Please don't assume the worst when reading someone's comment.

Seems like one a situation where the language in one cultural context would be insulting, but in another, is merely a literal statement.

No, I didn't meant it. It's a too common mistake to make.