Moving will be made to interrupt spellcasting at a point in time...

[Mychael]

If we must have this feature, I say that rather than literally 0 movement allowed, we should get a fraction of a yalm. Why? It would stop the problems with inertia, help correct for lag, in case the game doesn't get the message until just a tiny bit too late, and not make anything worse. Frankly, if moving half a step in walk mode will put you out of range for something... you had just as much of a chance to be out of range to begin with. I'm barely talking a full "step" (unless you're a lalafell)--just a little something--definitely not being able to move away from anything

Personally, I would like a complex system rather than black-and-white. Since you asked, Phe, some different ideas of mine would include...

• Different rules for different spells.

• A low-level spell could be cast while moving for a heavy penalty to magic accuracy, enhancing magic, and healing magic (e.g. a 50% chance your attack/enfeebling magic would miss, a 35% reduction to healing magic potency, and a 50% reduction to enhancing magic skill)
• A mid-level spell could be cast while moving with a heavy penalty to magic accuracy and magic attack and a heavier penalty to healing magic and enhancing magic. (e.g. 50% chance of miss, and -35% damage; -65% "Cure" effect; -80% enhancing magic skill)
• High-level spells would not be castable while moving.

• Based on difference between your level and the spell's level.

• You could cast a spell 10 levels below yours while walking, but not running.
• A spell 30 levels below your level can be attempted while running.

• Being hit while running and casting has a 30% chance to inflict a 2 second stun effect on the caster.
• An ability that allows you to cast any spell at full potency while moving with a 25% chance of reflecting 50% of the damage onto yourself.

Etc.