Second off, I believe we were trying to help the OP's problem of getting rid of the stale icon with the M being displayed while in the "User Macro" window, not the tooltip of the action on the hotbar. Which doesn't seem to be the case since the limited number of preset icon choices eliminates ACN moves and most likely a few SMN and SCH too though I haven't checked.

Thirdly, /macroicon "ability name" and /micon "ability name" work exactly the same for me, neither one show's the tooltip help on mouse over and I'm sure it just may simply not have been implemented yet. As for my I only care to see the GCD as well as the proc from other abilities and/or combos. I don't feel the need to have it as I know what the icon's tooltip does already but I suppose with would be nice to hover over it as a reminder for job/class swapping without having to pull up the ability list.