I like the new ending markers (the unselectable/uneditable "// ClassName" markers at the end of closing parens/braces), they're helpful information.
However, when I first saw them, I was VERY confused as to who had added all of those comments, and why I couldn't modify them.
Can we simply make their format be configurable in the color scheme preferences so that they don't have to look exactly like comments? I'd really like to make them a lot "dimmer" than my comments so I can tell them apart. I looked for the selection in the formatting preferences, but I couldn't find them.
I'd prefer them to not look like comments at all.
Perhaps something like how TypeScript shows names of method parameters.

cc @alexander-doroshko @jwren
Kudos on this. I'd also add that even though they are unselectable/uneditable, they still bump your cursor to the end of them. Would be great if that were not the case.
We've gotten this feedback from other sources as well. For the record they can be disabled from the Editor ? General > Appearance page (under the dart closing labels checkbox).
I think we should:
Filed an issue against the Dart plugin here: https://youtrack.jetbrains.com/issue/WEB-31828
From recent studies, we found participants appreciated this helpful IDE feature, but one participant initially thought those auto comments are the actual comments.
cc: @jayoung-lee
The closing comments feature may now be superseded by the new UI Guides feature.
The above issues with closing labels still exist
1) They still interact with the cursor, causing it to hang at a position after them (as though the labels existed for editing) until you press a key. The actual keypress shows up in the wrong place, and then suddenly does a jig to the left to the correct position (before the label)
2) They still look like comments and are styled like comments. I would suggest they have separate styling.
If the UI Guides mentioned in the prior comment are the vertical bracket lines, that's fine when the display list is short, but once it gets taller than the screen, the closing labels are helpful.
Thanks. 'Interacting with cursor' has been fixed. It won't be possible to put the cursor after a closing label (unless Settings -> Editor -> General -> 'Allow caret placement after end of line' is enabled).
Customizable appearance is not implemented, tracked as https://youtrack.jetbrains.com/issue/WEB-31828.
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Kudos on this. I'd also add that even though they are unselectable/uneditable, they still bump your cursor to the end of them. Would be great if that were not the case.