Okay so if I'm reading this correctly, and I've read this in the rule book and was kind of confused when i first read it, then this situation would be a travel for "touch(ing) the floor with a knee or any other body part of the body other than a hand or foot." (4-44-5a)

Suppose a defender dives to intercept a pass and catches and holds it, similar to an airborne soccer goalkeeper diving for a shot in the upper corner, then he lands on the floor. This would be a travel.

In my mind, this seems like an unfair punishing of a good play to maintain possession. A player can catch and land on his feet and its not a travel. He can even land on one foot, jump off of it, and land on two. But according to this rule, if he lands on his body in a 'thud' and not move after hitting the floor, this would be a travel.

Is this thinking correct? And while I know we are only supposed to enforce the rules, does this seem like something that wouldn't be intended by the traveling rule?

Completely wrong. What scrapper posted is completely true, by rule. If you gain possession while diving, it's a travel when you hit the floor. Geeze they cited and printed out the case play for you already in this thread to prove that. Didn't you read it? Case play 4.44.5SitA.

If you gain possession after landing on the floor, you can finish sliding, rolling, etc. That's case book play 4.44.5SitB.

Correct, it's a travel.....and it's explicitly intended to be a travel by rule.

What's a loose ball?