Both Uses

tact
in
A Prayer for Owen Meany
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And Simon rather tactlessly, but innocently, added: "Who would have thought he could hit a ball hard enough?"†
p. 140.3 *

tactlessly = in an offensive manner

standard suffix: The suffix "-lessly" in tactlessly means in a manner that is without. This is the same pattern you see in words like harmlessly, fearlessly, and remorselessly.
He was very good at that part of it—very respectful of grief, very tactful (while at the same time he managed to be very specific).†
p. 443.6

tactful = to say or handle things in a way that makes others feel good about them

Definitions:

(1) (tact)
the ability or act of saying or handling things in such a way that others feel good about them
(2) (meaning too rare to warrant focus)