Thank you all for your thoughtful responses.
The mixed responses sort of confirm my initial hunch that the seller would take my comment as an accusation of his misrepresentation of an item as a seller or as a poor collector.
I don't want to give the seller that impression. I collect old US stamps and frequently come across faults and some very novel attempts at repair. I think they are interesting and fun to share with other collectors. My comments to the seller would have been along those lines: "Ya know that tape you mentioned? Guess what, it's a very well done repair. Neat, eh?"
After reading your responses, I'm pretty sure the seller wouldn't take the comments in the spirit they were given. I'm going to keep my mouth shut.
I like stamps with "character." LOL For example, I bought this Scott 122 with my eyes wide open:
What at first glance looks like a smudged cancel on Lincoln's head is actually a repair. Most of the back of his head is missing! LOL Someone took the time to carefully ink in a 2-3 millimeter hole.
I know that greatly reduces the market value of the stamp. The seller knew it as did I. There was no misrepresentation. The stamp has character and a unique history that I appreciate.
Not everyone enjoys ratty old stamps. I need to keep that in mind!