In my opinion. You could offer help is someone ask for it.
Do you think people in that boards haven't already think about all the flaws they have, as you said. Do you think they haven't already an enough low self-steem for needing someone else recall them.

What do you think is better: help a person to recognising his/her values that (s)he finds difficult to see or keeping on pointing them out the flaws they are trying to overcome?

You only can give them opinions and for giving someone your opinion, you need to be open as well, to listen to them.

This is my honest opinion.