If someone is just repeating what they've heard, what they've read, what they've memorized, repeating the general consensus, not speaking from actual experience, then there is always a chance they could be misleading people with what they say. I don't care how in depth one goes into the literature - how many years they've studied, how many degrees they have, how many books they've read, or how much Pali they know - if they aren't also learning to apply it, learning to SEE dhamma in their own experience, confirming what they've read in the books, and speaking from that sort of knowledge, how can they ever know if they know what they know?
So in a nut shell, unless you've seen the things you are saying, you won't know if you are misleading others. The speaker - if he or she is so inclined to admit his or her possible shortcomings with his or her knowledge of a particular subject - can, most courteously, protect the listener with a simple disclaimer. For example: "As far as I have come to understand..." or "As far as So and So has said..." or "According to such and such a source..." or any variation, can help the listener's understanding remain dynamic and open to adjustment.
EDIT - This is just my opinion