This constant trend to use salutations (Sir, Dear, Respected) is also a cultural difference.
Oh, is that a cultural thing? 75% of my inbox at any one time is full of people calling me "sir", but I'd assumed that these people were just taught to be ultra-polite when they were learning English (maybe due to a delay between the real world and instruction vis-à-vis shifting politeness standards over the last ~century).
The first few times people used unnecessary politeness like this on me, I found it amusing. I was thinking, "who do you think I am, the president? LOL." But I've now grown to associate it with clueless people...
As jackg mentioned, English is a fluid and forgiving language. Even on a pretty global forum like this, I only rarely see English so bad that I can't understand it at all. As long as you actually
have some ideas to express, you should be fine. You should keep in mind that poor English is more difficult to read, though, so if you know that your English is imperfect, it'd be courteous to keep your text to-the-point, and to do some extra checking to minimize errors as much as possible. (I do the same when writing imperfectly in my second languages.)
A good recent example which comes to mind is zentdex's
Where the merit pours. He made several English errors, but he was entirely understandable, and the post was overall a very good contribution.
The real problem is people posting nonsense just to post, with no real contribution to make or ideas to express. That's bad enough as-is, and poor English makes it even worse.