Has anyone actually asked if it was an Honorblade? I know all the evidence points to this, but if we are missing part of the story, perhaps it comes from a false assumption such as this. We know Brandon has said we've seen 3 types of blades in TWoK, and knowing that we saw a number of Shardblades, Szeth's Honorblade, maybe Taln's blade is the 3rd type.
Also, going off assumptions we've made, has anyone directly asked Brandon if someone besides "Taln" did anything to the blade? Maybe the blade mismatch from TWoK's Epilogue and when "Taln" shows up at the warcamps is something of "Taln's" doing, and not by an external party like we have been assuming.