Interesting, seems pretty similar to an Executive Summary which also would have been very useful here.

But no one knows what that means, so you would have to explain the whole thing every time you use it, defeating the purpose of a short acronym.

Say tl;dr in the first sentence and everyone knows what it means.

>But no one knows what that means

... anyone with writing experience in the military knows what that means.

So still relatively few people.

No, you don't label them you just follow good writing practice and put the important details first, details and data second

A TLDR is traditionally at the bottom, but there's no rule against putting it at the top.