There is a warning comment in the views-view-fields.html.twig template:
<!-- THIS FILE IS NOT USED AND IS HERE AS A STARTING POINT FOR CUSTOMIZATION ONLY. See http://api.drupal.org/api/function/theme_views_view_fields/8 for details. After copying this file to your theme's folder and customizing it, remove this HTML comment. -->
It would be better to make this a Twig comment instead of an html one, because right now it will appear in the page markup when someone uses the template in their theme.
It says to remove it, but I wouldn't be surprised if someone forgets. Lets not penalize someone for overlooking this and ending up with it in their markup.
I checked the issue where it was added, and there is no mention of why it was added this way. (There isn't even any specific talk about adding it at all.)
Leaving it in, instead of removing it completely, is fine. The warning is correct, but it doesn't need to be visible to a site visitor.
Beta phase evaluation
|Issue category||Task because nothing is broken.|
|Issue priority||Not critical because it is basically a documentation change.|
|Unfrozen changes||Unfrozen because it only changes a template and documentation.|
PASSED: [[SimpleTest]]: [PHP 5.5 MySQL] 101,420 pass(es). View
PASSED: [[SimpleTest]]: [PHP 5.5 MySQL] 101,446 pass(es). View