Let's have a go at formatting your question more correctly:

I have recently come across several questions, in English, which are grammatically incorrect. 

While the English itself is generally alright, there are many typographical errors and, worse 
still, spaces before - instead of after - punctuation, or no spaces at all, and no 
capitalization at the start of sentences.

It is hard to believe that the OP does not know how to use punctuation and spacing correctly, 
so either they think this some sort of 'cool style', or they are lazy, which I consider 
disrespectful to everyone else visiting SO.

What is a good way to tell them, in a firm but friendly manner, to improve their grammar? 

I would not want to downvote on such a triviality.

Should I simply edit and fix the question, hoping that they see the difference? 

What might be an appropriate, short comment, possibly with a link?

One of the great joys of English and, I suspect, a reason for its proliferation, is its tolerance of precisely such abuses. Long may they continue.

Let's have a go at formatting your question more correctly:

I have recently come across several questions, in English, which are grammatically incorrect.

While the English itself is generally alright, there are many typographical errors and, worse still, spaces before - instead of after - punctuation, or no spaces at all, and no capitalization at the start of sentences.

It is hard to believe that the OP does not know how to use punctuation and spacing correctly, so either they think this some sort of 'cool style', or they are lazy, which I consider disrespectful to everyone else visiting SO.

What is a good way to tell them, in a firm but friendly manner, to improve their grammar?

I would not want to downvote on such a triviality.

Should I simply edit and fix the question, hoping that they see the difference?

What might be an appropriate, short comment, possibly with a link?

One of the great joys of English and, I suspect, a reason for its proliferation, is its tolerance of precisely such abuses. Long may they continue.