OK - so Low makes a point of saying "honesty" not "truth" - however:

In a court of law one would be asked to speak the truth, nothing but the truth and the whole truth - and I would say that living this principle, emotionally as well as in words and deeds, would be honest.

So if the question is reduced to "does it exist?", I'd argue that yes, some fraction of percentage of sentient beings on this planet are enlightened enough.

However as a consistent behaviour between humans? At least the latter part (the whole truth) is often sacrificed to "being tactful" and "not wanting to hurt feelings". Now this may be very good reasons given some circumstances - which would then mean that in inter-human communication consistent and total honesty, while being theoretically possible, is a Pandora's Box, which we have learned to fear - and therefore avoid?

In times of crisis it is of the utmost importance not to lose your head (Marie Antoinette)