See http://perfectionkills.com/the-poor-misunderstood-innerText/ - innerText is a nice property for getting HTMLElement text as presented, the same as you would get when selecting the element. Its behavior should be standardized (and implemented in Firefox).
I think, more than / before specifying selection behavior, it’s crucial to specify plain-text style normalization behavior, which would then be used as part of selection behavior (which also entails things like element boundaries and such, which, while important, don’t affect the behavior of innerText).