I would appreciate some attempt to derive a line drawn somewhere stating 'a substantial portion of the community deems this unwise and/or unbalancing'.
For what it's worth, here are my thoughts on how to start looking for this line:
Data point 1: The most basic use of an aspect is to turn a fate point (or a free tag) into a +2 to a roll. It seems to me that this sets a reasonable baseline for how effective other uses of aspects should be -- that is, "not much more than two shifts".
Data point 2: A maneuver allows you to convert an action into an aspect plus a free tag. Reverse this to see that spending that tag to cost a character a lost action is well within the bounds of reasonability.
Data point 3: For attacks and consequential contests, invoking an aspect can be countered by a mild consequence (a severe consequence counters the effect of three invoked aspects). So it seems fair to say that an aspect generated by a maneuver probably shouldn't be much more "severe" in nature than a mild consequence.
Note that I'm not trying to say that an invoke-for-effect or compel need be restricted to exactly two shifts of effect; I'm just trying to establish a sense of scale. Using a maneuver to inflict
Shoelaces tied together on an unsuspecting victim, then making them trip and lose their first action of an ensuing combat seems reasonable. Inflicting
Throat ripped to shreds by maneuver then invoking it to cause death by strangulation/blood loss is not reasonable.
Note also that any time an aspect is used to trigger a compel, the victim always has the option to say "Nah, I'll just buy off the compel. Having my entrails ripped from my stomache and tied around the fire hydrant by your maneuver last exchange doesn't complicate my life". Perhaps that should be a "data point 4"...
It might also be worth taking another look at the section on maneuvers on YS207, which says the following that is relevant to a discussion of the 'power level' of a maneuver:
* You can use maneuvers to gain momentary, situational advantages in a conflict
* It doesn’t have a lasting effect on an opponent, but it sets up a condition that will make a future attack more effective
If you are trying to do more than the above with a maneuver (like cause death), then you might want to consider a different mechanic, like an attack.
So -- using water magic to fill someone's mouth with water. I think that any of the following would be reasonable:
* Maneuver placing "Choking on water", which could be tagged or invoked to cause the victim difficulty due to the effects of the spell. This might include losing an action while gagging and trying to spit the water out. Or possibly taking a two-stress hit instead. Or just spending a fate point to avoid being inconvenienced.
* Grapple attack, which would cause extending incapacitation and a 1-stress hit per exchange until the victim manages to break the grapple or the spell wears off.
* Normal attack, inflicting damage as normal (or possibly using the special-effect attack rules on YS326 to do a mixture of damage and the above).
At least, that's how I look at it.
