I've noticed spells that change targets (shunt, redirect, etc.) have gradually shifted from blue to red over the years. I was wondering what the logic was behind that change. Was it a conscious choice or did it sort of happen organically?

It’s something we let Blue and Red do. Red just has less spell effects so I think it uses it a touch more.

To quote one of your most common phrases, "if your theme isn't in common, it's not your theme." How does this statement apply to red and it's issues with mechanics at common? Obviously not every mechanic can be placed at every rarity, but maybe by expanding the common presence of certain of red's higher rarity mechanics (Shunt/Reverberate) in a similar way to how counterspells are handled at common will allow people to get the feeling that these effects are part of red's broader identity.

The problem is those mechanics just aren’t common mechanics. Also, regarding my quote, those effects are not supposed to be red’s most defining effect, direct damage is- and that’s all over common.