Brutal honesty does not work for me, I'm tactfully honest. I obfuscate or downplay the truth when I deem it necessary, and sometimes I opt for socially acceptable answers instead of the truth, because the raw truth will just hurt the other person unnecessarily.
For example, I wouldn't hypothetically tell my partner he looks fat in his new pair of jeans, I'd tell him I like his other pair better on him.
I won't tell my best friend I think her husband's a vile excuse for a human being, I will let her know how amazing I think she is and how she doesn't need him to validate that.
I like this post relative to the OP because it reflects a trait some of us on the spectrum have more than others- cognitive flexibility. An executive function reflecting an ability to think about various things in more than only a "black and white" fashion. To be able to qualitatively "interpolate" what lies in between and to know when, where and how to do it.
Yet I think for anyone on the spectrum, it's necessary to understand that such abilities with cognitive flexibility can potentially vary greatly.
That for some honesty isn't something they can necessarily "practice" at will, but rather more a case of simply having no options neurologically speaking of mitigating truth when it might constitute a matter of kindness or pragmatism in the larger scheme of things.