I don't necessarily feel that appearances matter more than reality, depending on what appearance you are referring to. We're talking about resumes here (or at least I am), and we're in an industry where some (often the young) have opinions about the older members of the industry. This isn't new, and it's not even specific to the industry.
The reason I'd suggest trimming the resume is so you can actually be invited in to have that conversation where you can then convince someone who might be ageist that their bias is incorrect. By including information that makes it obvious you are of a certain age (for some it could be 30+, 40+, 50+, 60+), you are giving someone the ability to discriminate.
It goes the other way as well. Workers in their early 20's might want to appear (on paper) as old as reasonably possible.
The reality is that lots of older workers know their stuff, and will only be able to change the minds of those who discriminate by getting in front of them. I'm not suggesting "by any means necessary", but I have on issue with the tactics I suggest.
1 - http://jobtipsforgeeks.com/2013/01/31/ageism/ (Overcoming ageism) http://jobtipsforgeeks.com/2014/03/25/older/ (Why Hire Older Engineers)
