Well, to add to all of the helpful answers I got in this thread

, I'll post what happened.
I really want to buy some stuff (okay, a lot of stuff for an upcoming cruise

) from Jessica London, which is a catalog & internet retailer associated with Chadwick's. However JL does not participate in many programs (only MyPoints, I believe, at their measly 2 points per dollar), whereas Chadwick's is almost everywhere. So first I emailed Chadwick's customer service and verified that yes their GCs could be used at JL (or vice versa, if you want).
Then I went through the GoldPoints site link to Chadwick's, bought the GC, and lo and behold the points show up a few days later in my GP account! Now I just have to wait for my paper GC to arrive via snail mail -- no other option presented -- and then use its number on my JL purchase. Voila! GoldPoints on a Jessica London order!
Since all affiliates (ebates, GP, etc.) use the same commissioning structure, this scheme would surely work with any point/rebate portal, at least with Chadwick's.
Still wondering about other retailers "paying" on GC purchases, though....! Anyone thought they'd get their rewards and didn't?
Now to spend my "gift" to myself...!
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An infrequent flyer trying to change that by earning my miles via alternate methods!
and webmaster at
http://www.RewardsLookup.com