How is feedback process done after submitting an article to arXiv? Another arXiv related question...

In several posts I have seen people talking about getting feedback after submitting article to arXiv

I have never submitted anything to arXiv before, so I have no clue how this is done. Is this just an informal procedure whereby other researchers in your field email you about your article?

Or is there a formal feedback process submitted through arXiv? Is this for available for public viewing or discussion? 

How exactly is this done? Thanks!
There is no official protocol or formal procedure. Here is how I handle it. 

I skim the arxiv submission in my fields of interest every day (headlines and abstracts). Every few days I find some things that I read in greater detail and if it happens that I find something that I'd like to discuss with the authors, I write a joint email to all of them. Could be a question for clarification, a hint for further reading or something like "look here, I've done something related". Once in while I take the time to write a blog post for some article and then it sometimes (rarely) happens that one of the authors comments on my blog.