Bender's Sword (Spoilers)

OK, I've gone through most of the topics on this board with people griping about inconsistencies and plot contrivances, but I haven't heard ANYBODY mention the most perplexing bit about this movie.

The way that Yivo finds out that Fry communicated with Bender is because for some totally unexplained reason, Bender has Fry's letter (on pink paper) attached to the edge of his sword. WHY??? What reason would Bender possibly have for attaching Fry's letter (which he's already read, and seems to be torn to pieces) covering the edge of his sword?

Not the handle, not the back edge, but the presumably *sharp* edge of his sword! Wouldn't that make the sword dull and therefore useless? Bender's not typically known to be the sentimental type, but if he kept it for sentimental reasons, why would he have torn it to bits and attached it to the edge of his sword instead of just keeping it intact?

It seems the ONLY reason it was there at all was as a poorly conceived plot device to facilitate Yivo's reaction and feelings of betrayal. I'm just amazed that nobody else has pointed this out yet!

For what it's worth, this movie was OK, it had its moments for sure, but definitely not as interestingly complex or well-written as "Bender's Big Score". I sure hope the next two are better than this one.