If a creature loses and then gains an ability (Turn to Frog is cast on it; Deep Freeze becomes attached and then unattached to it; Mirrorweave temporarily turns it to something else; Ixidron turns it face-down and Ixidor, Reality Sculptor turns it face-up again), is it regaining the same ability or a new instance of that ability? Do one-per-turn restrictions (Rootwalla) still count as having been activated, and are linked abilities (Angel of Serenity, Tidehollow Sculler) still linked to their original instance?

I'm 99% certain that the answer is “it's the same ability,” but I can't find comp rules support to definitively prove it.

Edited Eli Meyer (April 23, 2018 03:50:26 PM)

Your understanding is correct. Effects that remove abilities (or make copies) that then expire (or turn things face-down that later turn face-up again) don't break linked abilities, nor do they reset activation restrictions. When the effect expires (or the creature turns face-up), the creature isn't gaining a new instance of its abilities–it's just having the same old instance of the ability revealed once more.

It's useful to think about effects that remove abilities (or make them disappear in other ways) as acting like correction fluid or tape–they “remove” the ability by covering it up and rendering it invisible, and when they expire, they disappear, revealing the same ability that was originally there.