I would treat this with extreme caution. I certainly cannot claim to be a Houdini expert but I do own a couple and I researched his autograph quite a lot around the time I bought them.
To me the OP example lacks a certain looseness and looks too uniform, especially the HHs. I also don't think the HHs normally look so much like flamboyant AAs.
Here is one of mine that dates from around the same period and a much earlier postcard that I once tried to win on eBay:
Not a Houdini expert but autographs themselves were not a popular hobby when this would have been signed. Then to have a Comic Con like quote added to it? I doubt it. If it was more of a letter or something written directly to the person like you see in Pugs examples that would make it more believable.