Things like this are just ridiculous plot contrivances that the writers never bothered to think through.
Can somebody who understands how these shows are actually made explain who really deserves the blame for this kind of thing?
Us nerdy fans, for over-analyzing a fictional shapeshifter's physiology.
Seriously. It's implausible to think a Klingon could kill Odo with a sword. But, since the writers purposefully avoided going into detail about the mystical mass-altering magical morphing security guard's anatomy when he's in humanoid form, it's not impossible. The director/writers probably just went with which weapon looked better.
And Photon, condemning the entire series as having FUBARs and lazy writing because of something as minor as Odo getting cold-cocked in an early episode is a tad melodramatic. And thinking that giving DS9 Star Trek XI treatment would reduce
plot inconsistencies is utterly laughable. DS9 is thousands of times more consistent than that movie, entertaining though it may be.