GNOME 3.10 Released

"The problem is not accidentally selecting while middle-clicking, but accidentally selecting while clicking normally. For example, you might click the address bar, hold down backspace to clear it (itself very irritating, as the more natural "triple-click and hit delete" idiom will also blow out your copy/paste buffer), then middle-click in the blank address bar."

You are attempting to use this like a two-step copy paste and it just isnt. So forget about your copy/paste buffer, that isnt even involved in the yank. You have to clear the space before you start, since there is one step, not two, it is not possible to insert a step between the steps, when there is only one step.

"A more common problem, for me anyway, is that I have a habit of (a) selecting text while reading long pages as a way of bookmarking my position while scrolling or checking other windows, and (b) selecting text to delete/overwrite it. It is frustrating that both these activities lose data from the paste buffer, especially when trying to overwrite text from the clipboard."

But they dont. The paste buffer is unaffected. You access it with shift-insert or ctrl-v or meta-v or whatever you have that mapped to - the middle shift yank uses the primary selection, NOT the paste buffer!