A clear and concise description of what the problem is.
I caught myself a few times marking someone who I didn't mean to mark because right before I right clicked, the list updated and the order of players has shifted.
Describe the solution you'd like
Freeze the state of the player list when the cursor is within that list.
Describe alternatives you've considered
Nothing comes to mind.
Additional context
I realize the name of the player shows up in the context menu that opens up after rightclicking, but I admit, when I'm marking someone while waiting for a respawn on a short timer (or, worse, briefly mid-life when behind cover), the thought of double checking that name slips my mind.
With this feature implemented, there would be less reason to do that check. Unless you have bad aim, I suppose.