"Even lying can be for protection at times."

Oh for sure. But the idea (to me) is, if you have am honest online community with lots of trust build up, you don't need to.

"do you really think that you can force people to choose a profile picture that represents them accurately"

Of course you can. But that does not mean it is a must. That depends on the specific rules.

"You may want to look up the definition of 'lying by omission'. Within the context of asking for profile information, it might well be"

But not with the examples you gave.

I will check out the paper later, but I doubt I will learn much new. It is not a new topic to me.