As a rule of thumb you should keep line length to 80 characters. In Vim you can display where the boundry is with:
Nothing, of course, stops you from exceding that number:
You can quicky shorten (wrap) lines to 80 characters using
gq format tool. I'm using par for this purpose.
The text from the screenshot was formatteed with (from line
(reformat text to the end of file)
It works OK, but it's still not readable. Fortunately with Dr. Bunsen
formd tool you can switch between reference and inline urls: