Gentlemen,
Thanks for all the ideas and suggestions. After reading your responses as well as some info I found in a FAQ on Aimpoint.com, I think that this sight is OK and the problem is me, which was what I was tending to think all along.
I tried the sight with both eyes open, then left, then right -- all the same. As Aimpoint suggested, I rotated the sight while looking through the reticle, and the dot does not change at all, which indicates that what I'm seeing has something to do with how my eyes are working. If the dot did change aspect in conjunction with the rotation, then it would indicate a mechanical defect, but no, it stays the same.
One thing I noted is that I found myself focusing on the dot, not on the target (in this case, a marked spot on a white wall). When I focus on the dot is when my problems mainly occur -- if I focus on the target (which is what I should be doing anyway with this gadget), the dot then assumes a single, rounded shape. I'm thinking that my lifetime of using iron sights, where the focus was always on the front post, has developed in me a habit that is not to be used with the Aimpoint, being a different sort of aiming device entirely.
I'm going to a big gun show here in Florida the weekend after next (Lakeland Rifle and Pistol Club -- yeah!), and I will take the opportunity then to confirm my findings. But for now I'd have to say that this is more a result of me focusing on the dot rather than the target. Embarrassing, but true. I thank you all for taking the time to help me figure this out.
Stay safe,
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