First of all, I think Vern expressed somewhere very explicitly that ladder jumps remain a feature of the Original game.
Now, as for removing it or not from the Sequel: I've always felt that, amusing and sweet though it is, it doesn't really look like a legal move. Now I'm all for illegal moves in Custom mansions, but I wouldn't support them in the Official ones.
So of course Vern can decide to ask builders to abstain from using compulsory LJs in Official mansions, but these would be free of use for custom mansions. However, the possibility for a player to use ladder jumps anyways also allows for shortcuts and quick-and-dirty solving of puzzles, most strikingly in some of the Gold-and-Silver sections. To prevent this, the designer has to either decide it doesn't matter, or make the mansion ladder-jump proof which can be at best cumbersome.
So while ladder jumps certainly increase the amount of possible puzzles, they also put limitation in puzzles from the other side.
Also, as long as ladder jumps are not officially mentioned in the Tutorial, there is no reason to assume a player would know it exists at all -- unless he or she's a regular forum visitor. (BTW [wishful thinking alert] are there statistics regarding the estimated number of players vs. people who visit the forum, even without registering?)
A possibility to take the best of both worlds, and here
possibility
is taken in a very loose sense [in other words, Vern would have to do all the work], is to allow ladder jumps for some types of ladders and not the others. Like, Jack can jump from broken ladders, but not the whole ones.