Is it forbidden for a non-Kohen to form the hand formation that Kohanim use during their priestly blessings?
I was at a different shul this morning, and while flipping through Halachically Speaking, vol. 1 by Rabbi Moishe Dovid Lebovits, I saw a paragraph about this very issue. From what I recall, he wrote that while the Zohar discourages people from forming their hands like the kohanim, poskim have taken this to apply only during the time of the kohanim's blessing.
The author concluded by saying that in practice, one should refrain unless it is being done for educational purposes.
I know of nothing in halakha that says that it should be. Whereas the AriZal, the RaShaSh and the Ben Ish Hai, all claim that to a certain extent the same hand gesture should be assumed when a person washes his hands in the morning or for bread, and when raises their hands at the posuk Poteah Et Yadekha in Ashrei. The notable difference(according to some) being that the palms face onseself as opposed to facing outward. However, the Ben Ish Hai also states that palms should face the Kohen when he blesses so by him the gestures are identical.