A card that is currently revealed may be revealed again.
July 3, 2020 · Core Set 2021
If an effect would cause a player to shuffle one or more specific objects into a library, that library is shuffled even if none of those objects are in the zone they’re expected to be in or an effect causes all of those objects to be moved to another zone or remain in their current zone.
September 30, 2016 · Kaladesh
rule 701.20c not present in this release
September 30, 2011 · Innistrad
A player wins a clash if that player revealed a card with a higher converted mana cost than all other cards revealed in that clash.
June 17, 2011 · Commander 2011
A player may planeswalk as the result of the “planeswalking ability” (see rule 309.6) or
April 1, 2011 · Duel Decks: Knights vs. Dragons
A player may planeswalk as the result of the "planeswalking ability" (see rule 309.6) or because the owner of the face-up plane card leaves the game (see rule 901.9).
February 4, 2011 · Mirrodin Besieged
A player may planeswalk as the result of the “planeswalking ability” (see rule 309.6) or because the owner of the face-up plane card leaves the game (see rule 901.9).
October 1, 2010 · Scars of Mirrodin
A player may planeswalk as the result of the “planeswalking ability” (see rule 309.6) or
February 1, 2010 · Worldwake
A player may planeswalk as the result of the "planeswalking ability" (see rule 309.6) or because the owner of the face-up plane card leaves the game (see rule 901.9).