It always seems to me that any little disclaimer about my degree of certainty seems to disproportionately skew the way others interpret my statements.

For instance, if I'm 90% sure of something, and carefully state it in a way that illustrates my level of confidence (as distinct from 100%), people seem to react as if I'm substantially less than 90% confident. In other words, any acknowledgement of less-than-100%-confidence seems to be interpreted as not-very-confident-at-all.