2013-06-07 : Dredge lets you replace any card draw, not just the one during your draw step.

2013-06-07 : Once you decide to replace a draw using a card’s dredge ability, that card can’t be removed from your graveyard “in response.” (Replacement effects don’t use the stack.)

2013-06-07 : You can’t use dredge unless you’re going to draw a card and the card with dredge is already in your graveyard.

2018-12-07 : Because damage remains marked on a creature until it’s removed as the turn ends, nonlethal damage dealt to Golgari Grave-Troll may become lethal if you return remove +1/+1 counters from it during that turn. In this case, it dies before you can resolve the activated ability that will regenerate it.

2018-12-07 : If you return Golgari Grave-Troll from your graveyard directly to the battlefield, its first ability counts itself.