Signal in a more obvious way that a highlight has been created

There are a lot of duplicate highlights in the database. To see the phenomenon, use https://metabase.hypothes.is/question/759 on the default URL for that query, https://www.theatlantic.com/magazine/archive/1945/07/as-we-may-think/303881/, or another heavily annotated URL like https://www.nytimes.com/2007/02/19/arts/design/19fram.html.

The query reports the start and end value for TextPositionSelectors, and focuses on highlights. It reveals that it's fairly common for highlights to occur twice: same user, same target, same time, but two or more distinct annotation ids in the database.

Some examples:


I'm pretty sure I know what's happening here. When you create a highlight, the only feedback you get is that the target, which was highlighted in one color before you clicked the highlight button, is now highlighted in a different color when the button goes away. There should probably be some other, more affirmative, and non-color-related way to signal that the highlight was created.

(The reason for this odd discovery: I was working out ways to analyze document hotspots, i.e. regions in documents that attract overlapping annotations.)