If/when more "reveal your hand" as a cost/additional cost like Land Grant? It feels like a neat design space . (All for it being used as additional cost over more free spells though)

Probably when, but it has issues. We generally like hidden information and it isn’t that much of a cost to pay.

How come cards like the “will” cycle from commander legends or the free spell cycle from commander 2020 say “if you control a commander” and not “if you control your commander”. The VAST majority of the time these are the same thing, so I’m curious why it was decided to have them be worded the way that they are

Sometimes templates change over time.

What would you say is the most dangerous effect to get costed wrong? Mana reduction/free spells or card tutoring?

The former.

Hi Mark! My birthday was this past Saturday, and as per the rite of Birthday trivia, I would like to ask about any trivia pertaining to Chronomancy or Chronurgy (Time Magic) as it relates Magic the Gathering, or, failing that, some trivia on my favored counterspell "Rewind". Thanks!

In Urza’s Saga, I made the “free mechanic” as an alternative to doing cantrips. (At the time, we weren’t allowed to have them in every set.) Rewind was me applying the mechanic to a counterspell. The “free mechanic” would prove to be horribly broken, but it appears there’s one case where it’s not - reactive spells (things you can’t just cast whenever you want, but only do it in reaction to something specific happening). So Rewind turned out to be a free spell we can reprint.
Happy Birthday!

Mark, I played my dice rolling deck and activated my Wizard’s Spellbook rolling a 20 and casting two free spells, triggering Faridah for a card, Brazen Dwarf for damage, and Feywild Trickster for a dragon. All on a single roll of the dice! That being said, I would like to request more black boarder dice rolling for my commander deck to really get it rolling.

I’m game to try. : )

Hi, Mark. Did the Commander 2020 decks sold well for the line? Now that we’re close to the Strixhaven Commander 2021 decks I’m wondering if the concept of pairing the decks with a set’s theme worked well for sales (beyond the free spell cycle).

The Ikoria experiment, tying Commander decks to a product, worked very well.

Can you give an example of what you would consider to be mistakes made by vision design?

A lot of these are technically early design as they predate vision design.“Free spells”Odyssey being too Spike-yKamigawa block making all rare creatures legendary. Lorwyn being race tribal and Morningtide being class tribalShadowmoor shifting tribal colors.Eventide shifting to enemy hybrid.Battle for Zendikar focusing too much on the war.Kaladesh not removing opponent’s energy.Amonkhet being overstuffed.Ixalan not having tribal glue.

Beautiful design can be undermined with development by over pushing or over costing cards. Is the opposit true that poor design can not be fixed with great devoplment?

Bad design can be unbalanceable. For example, making certain free spells (from Urza’s Saga block) could make them more powerful,

You said "don' t confuse power level of execution with the mechanic itself" that could be applied to affinity, dredge, delve, pitch spells, storm etc. I believe any mechanic can be made playable to current standard(name any format) power level, its the time and effort needed for development to make it work. I believe it is possible to make standard playable moxen and other power cards. Would you say the time and efforts to balance these effects are resource intensive to be worth it?

Not every mechanic can be balanced. For example “free spells” can be made stronger by raising the mana cost.

Which "Free" spells do you think are less broken, the Alliances ones (like Force of Will) or the Urza's ones (like Rewind)?

The Pitch spells (the nickname for the Alliances’ cards) are less broken than the Free spells from Urza’s Saga. Less is the optimal word. : )