They require a sacrifice each time they're cast, and Riddle can't sacrifice his ability to love every time. The sacrifice the "new horcrux" ritual calls for is most likely a human sacrifice, meaning whoever you've murdered in order to create it.
You have a point, though there's no need to. I know I wouldn't, since I can't see what benefit would come from it. Specially if they figured it out between arcs (since there were no discussion threads active, or nearly none at least.) But probably at least a few would've said it and taking into account how many people would've needed to figure it out for that to account for the reduced number of comments, it's strong evidence against it. Sorry, I guess I didn't think it through too much.
This could explain the reduced number of comments. As Alsadius pointed out, there used to be 500 comments per chapter, so it stands to logic that as the series advance more users figure it out and stop commenting so as not to spoil it.
Can't you? If I recall correctly, Harry tried and failed before succeeding with Partial Transfiguration, while he was still thinking in the terms of atoms. Also, you could consider transfiguring air as a partial transfiguration unless it's within a closed system, since you can't think of air as a whole or defined object. So it stands to consideration that Harry might be able to do it using the model of timeless physics like he did to achieve partial transfiguration, since we have no proof that he tried again afterwards ( that I recall ). Still, this wouldn't be the best moment to try it.
Besides, could've just tried to levitate the gun or something towards the gun he could use as a shield, and run away or retrieve his invisibility cloak or used the spare turn on the time-turner... There are countless possibilities. Even if he did appear on the corridor one hour before, when only Snape was there, he could probably convince him of acting as he did towards him... Which would've opened the possibility of another Harry hidden somewhere ready to try to take down professor Quirrell, or rather a Harry who had already sent a messenger Patronus to Dumbledore so he could quietly and without disrupting the Quidditch match take down the very charming Defence professor. Actually, this could still happen if Harry somehow retrieves his time-turner, or even if Cedric is hidden in Harry's pouch and uses it ( though I'm not sure how this would turn out... )
Why, I was resigned to a bad or unfulfilling ending, so this completely blew my mind. It's... perfectly fitting, and it brings back the pacing the story had earlier on in a beautiful, almost subtle way. I absolutely loved it.