Flyertalk Posting Legend Moderator: Credit Card Programs, American Express, Capital One, Chase, Citi, Diners Club, Eco Travel, Signatures
Join Date: Jun 2003
Location: Miami, Mpls & London
Programs: AA, IHG & Marriott Platinum; DL & HH Gold
Posts: 51,807
In my understanding HHonors, SPG, Skymiles, JetBlue etc are based on the Optima product. The terms of the Clear card are substantially different because this is American Express' "no fees" card. It makes sense that they would not permit an exchange to a card with materially different financial terms.
I would keep the Clear card, apply for HHonors, then use the online tool to move all except $1,000 of the Clear credit line to HHonors. There's no important drawback to keeping a dormant card that doesn't require an annual fee.