I do think that the exchange between @benkirk2 and @T_aquaticus was getting semantic (even tedious?) but Ben makes an important point about standing variation. Due IMO to a normal cognitive bias that plagues us mere mortals, we tend to think of evolution needing a particular mutation "just in time," so when we look backward at an evolutionary trajectory, we (again IMO) naturally tend to assume that the mutations happened at or near the moment they were "needed." This reasoning explains, for example, about 90% of Michael Behe's errors.
My view is that we exacerbate the effects of this natural bias by using the term 'mutation' to describe when discussing evolutionary change. The word itself means only 'change' but it has become strongly associated with 'deviation from the norm' and (largely through efforts to mislead) with 'damage' or disease. I believe this makes us naturally think that when a particular genetic variant became fixed in a lineage, that what happened was a lucky "beneficial mutation" occurred just when "an organism needed it." This is a constellation of errors.
Darwin, at least partly because he knew nothing of "mutation" and barely anything solid about genetics, built his case on variation. He rightly ignored the reasons for variation (which we now call "mutation") because those reasons didn't matter for his case. I suspect that people who follow Darwin's lead will find it easier to understand evolution. This, IMO, is also relevant to the excellent thread about barriers to understanding evolution.