And can it be eliminated? I find it distracting.
It looks to be a guide line, to suggest to developers to not write code that is too wide. Unfortunately, it doesn't appear to be configurable, so that it can be disabled like in other editors.
If you have a Github account, a suggestion is to file a request here:
(You could include link to this question as you have a helpful picture.)
It's the 80 character limit. The practice of keeping code to 80 (or 79) columns was originally created to support people editing code on 80-column dumb terminals or on 80-column printouts. Those requirement have mostly gone away now, but there are still valid reasons to keep the 80 column rule:
- To avoid wrapping when copying code into email, web pages, and books.
- To view multiple source windows side-by-side or using a side-by-side diff viewer.
- To improve readability. Narrow code can be read quickly without having to scan your eyes from side to side.
The last point might be the most important. Though displays have grown in size and resolution in the last few years, eyes haven't.
The origin of 80-column text formatting is earlier than 80-column terminals - the IBM punch card dates back to 1928. This is reminiscent of the story that the US railway gauge was determined by the width of chariot wheels in Roman Britain.
It is sometimes a bit constricting, but it makes sense to have some standard limit, so 80 columns it is.