Exceptions for copying are not implemented completely

>707.9e. Some replacement effects that generate copy effects include an exception that's an additional effect rather than a modification of the affected object's characteristics. If another copy effect is applied to that object after applying the copy effect with that exception, the exception's effect doesn't happen.

>Example: Altered Ego reads, "You may have Altered Ego enter the battlefield as a copy of any creature on the battlefield, except it enters with X additional +1/+1 counters on it." You choose for it to enter the battlefield as a copy of Clone, which reads "You may have Clone enter the battlefield as a copy of any creature on the battlefield," for which no creature was chosen as it entered the battlefield. If you then choose a creature to copy as you apply the replacement effect Altered Ego gains by copying Clone, Altered Ego's replacement effect won't cause it to enter the battlefield with any +1/+1 counters on it.

This one is bad because you could chain the copying to get infinite counters.

> 707.9f. Some exceptions to the copying process apply only if the copy is or has certain characteristics. To determine whether such an exception applies, consider what the resulting permanent's characteristics would be if the copy effect were applied without that exception, taking into account any other exceptions that effect includes.

> Example: Moritte of the Frost says, in part, "You may have Moritte of the Frost enter the battlefield as a copy of a permanent you control, except it's legendary and snow in addition to its other types and, if it's a creature, it enters with two additional +1/+1 counters on it and it has changeling." Moritte of the Frost copies a land that has become a creature until end of turn. It would enter as a noncreature permanent, so it won't enter with two additional +1+1 counters on it and it won't have changeling, even if it becomes a creature later in the turn.

_Wall of Stolen Identity_:
> 707.9g. Some replacement effects that generate copy effects are linked to triggered abilities written in the same paragraph. (See rule 603.11.) If another copy effect is applied to that object after applying the copy effect with the linked triggered ability, the ability doesn't trigger.