For me this behavior covered up valuable context above the selection (now under the popup) for a screenshot I wanted to take.

This behavior is extremely annoying for those who don't use it. Forcing the popup behavior makes the UX categorically worse for myself and many other users.

If Atlassian won't make the popups optional they could at least be consistent about the DOM element properties they use. I have created manual rules through my browser adblocker to kill these annoyances, but the rules constantly break due to churn in the HTML.

I agree whole-heartedly with the previous comments.  At the most basic level (as mentioned by @Martin | Zwerm), deviating from expected behavior should never be the default!

From a UX Perspective, anything that changes the default behavior of the browser should be optional. Please add a tick box to switch this off per user. 

Ditto for what Dave said. Our team will often visit Confluence pages while on video chat. Every time someone highlights text during a call it is a distraction. The presentation mode could be great if done correctly. I may look at plug-ins for this. I do not want my page transformed into slides though.

Lately, I have been giving informal tech talks with a Confluence page as my primary presentation material. I like this because my co-workers can just go to the page and use docs or other resources that I linked – which they are already familiar with because I will visit some of the pages during the talk. Before I start the talk, I disable javascript in my browser. This is the best work around that I have found and it breaks some pages that I visit.

For me, the pop-up interferes with team design discussions where we are using a Confluence page to discuss a software design (like a Power Point presentation).  I want to select different parts of the page for the people who I am sharing my desktop with when I am presenting...and the pop-up is super disruptive because it means you can no longer see the highlighted/selected text in context with the surrounding text...and it is distracting and not relevant.  Some type of "Presentation Mode" could be another approach maybe.  Basically, the pop-up is messing with a simple text selection action.  Pointing is less visual in a screen-sharing situation and also doesn't identify the key bits as explicitly.

Is it correct that this issue asks for a per-user option to disable the selection popup?

If so, that would be wonderful. This popup is very irritating for those who do not use the popup functionality.

Biggest issue - in a code snippet when double-clicking on a single word, Confluence selects the entire snippet instead of just the single word, breaking from normal browser convention. This makes it tough to select/copy parts of snippets.