What I meant was not that there are no tradeoffs to make if you want your character to be effective at both combat and things that aren't combat. Rather, as I said, there is no tradeoff, in the sense that you do not have make a single choice between being effective in combat and being effective at other things.
I don't understand how this can be true. Clearly, you've got to make a choice at some point. You could move that "effectiveness" slider toward combat, or toward non-combat, but you can't have it both ways, given that you have a limited number of points. I would understand if you said something like, "a 10% loss in combat efficiency is acceptable, given a 50% gain in non-combat efficiency"; is that what you're saying ?
The point is, if someone builds a character who is just really bad at combat, and justifies this by saying "but I'm a suave diplomat!", my question will be: how hard did you try to make this character combat-effective? Did you even try? ... There's no reason not to — again, unless you are specifically and deliberately make a combat-ineffective character.
That depends entirely on how you perceive the tradeoffs. Is a 10% drop in diplomatic efficiency worth a 50% gain in combat efficiency to you ?
I don't understand how this can be true. Clearly, you've got to make a choice at some point. You could move that "effectiveness" slider toward combat, or toward non-combat, but you can't have it both ways, given that you have a limited number of points.
Well, one way it can be true is if there isn't just a single slider. There could be multiple sliders. (In D&D, for instance, there's the Skills "slider", and the Feats "slider", and the class "slider", and the spell selection "slider", and a number of ...
There are things that are worthless-- that provide no value. There are also things that are worse than worthless-- things that provide negative value. I have found that people sometimes confuse the latter for the former, which can carry potentially dire consequences.
One simple example of this is in fencing. I once fenced with an opponent who put a bit of an unnecessary twirl on his blade when recovering from each parry. After our bout, one of the spectators pointed out that there wasn't any point to the twirls and that my opponent would improve by simply not doing them anymore. My opponent claimed that, even if the twirls were unnecessary, at worst they were merely an aesthetic preference that was useless but not actually harmful.
However, the observer explained that any unnecessary movement is harmful in fencing, because it spends time and energy that could be put to better use-- even if that use is just recovering a split second faster! [1]
During our bout, I indeed scored at least one touch because my opponent's twirling recovery was slower than a less flashy standard movement. That touch could well be the difference between victory and defeat; in a real sword fight, it could be the difference between life and death.
This isn't, of course, to say that everything unnecessary is damaging. There are many things that we can simply be indifferent towards. If I am about to go and fence a bout, the color of the shirt that I wear under my jacket is of no concern to me-- but if I had spent significant time before the bout debating over what shirt to wear instead of training, it would become a damaging detail rather than a meaningless one.
In other words, the real damage is dealt when something is not only unnecessary, but consumes resources that could instead be used for productive tasks. We see this relatively easily when it comes to matters of money, but when it comes to wastes of time and effort, many fail to make the inductive leap.
[1] Miyamoto Musashi agrees: