You'll have to show a case book ruling that convinces me of that "advantage-disadvantage" theory.

It's entirely conceivable that a defensive player can use something on the opposite side of the fence that prevents her from falling completely over. Heck, I've seen in MLB where fans keep players from falling into the stands. If that were to happen in a FED softball game, are you going to rule catch-n-carry then?

I'm agreeing with Manny here.

NFHS 5-1-i(d) says exactly that.

NCAA 9.3 Note 5 says the same thing.

Perhaps ASA is somewhat silent on the topic (or I can't find it :)), but I'm not seeing any ambiguity at all in the NFHS (or NCAA) rule.

And to me, that makes no sense. If anything, the foot being fully in contact with DBT is the definition of leaving playable territory.

And again, have you ever seen the OF touch the top or back of a fence and be ruled out of play?

Well, I just don't believe NFHS had all possible ways a fielder can touch DBT in mind when it came out with this rule. I posed some very plausible scenarios where a fielder touches DBT with her glove after making a catch.

We have a number of fields here where there is netting above the fence to prevent batted/thrown balls from going into adjacent fields or nearby traffic lanes. If a fielder catches a batted ball near the fence, and her momentum causes her to touch the netting with her outstretched glove, technically she has touched DBT. But I wouldn't kill play at that point.

I think the prevailing language is in the main part of 5-1-i:

It doesn't say "by touching" anything in DBT after making the catch.