I have not followed this thread, but I assume you are talking from the point of a zipless/glitchless run.
The rules I defined in
http://tasvideos.org/userfiles/user/Bisqwit (refined from the post at
http://tasvideos.org/forum/p/365009#365009) for a glitchless run of
Mega Man, original, was to categorically ban any manifestation of player-caused movement of Mega Man
faster than he could normally run or walk. Zips that cause him to momentarily move
slower are still fine, an example being a collision check instantly zeroing his subpixel component. This includes the example in your post above.
The most arguable application of this rule involves ladders. Ladders can instantly zip Mega Man both horizontally and vertically to align with the ladder, and this happens trivially in casual play even. When such movement speed exceeds Mega Man’s jumping speed (as measured by compared to what happens if up/down is
not pressed at that moment), it is banned.
The underlying guideline behind my rules is to ban any abuse of tradeoffs between the game’s perfect/correct behavior and code size/performance, whether intentional (as in “<developer> Yes, I know it’s not
exactly correct, but vast majority of players will never notice anything wrong, and fixing it would increase chances we run out of budget for money, ROM space, or production schedule”) or unintentional (as in “<developer> Oops! The game is not supposed to do that.”).