Why? I had trouble to find such nodes. Most of the time there seemed to be already enough answers or the node seemed so old, that it seemed irrelevant to answer.
If all you are going to do is repeat what has already been said, then there probably is no use in adding your answer. But, if you have something new to say on the subject, I'd suggest saying it. If the node is so old you are afraid your time will be wasted, consider whether it may warrant a small meditation instead. (I'd actually like to see some more mini- or even micro- meditations.)
On the other hand, some friends and colleagues constantly reported about questions not being answered at all, or not satisfactory.
This hasn't been my perception at all. I see relatively few nodes go unanswered, particularly if there is feedback from the OP clarifying the question when answers don't quite hit the nail on the head.
This "red flag" will indicate, that you are - in some way - unsatisfied with the answers you got.
I don't care for the "red flag" idea. Here's why... The current mechanism for this would simply be to re-ask the question. Or to engage those who try to answer your question in a dialogue. Asking the right question is often the whole trick and sometimes it takes some back-and-forth. Substituting a "red flag" for actual feedback would make the process more difficult for everybody. It would be like shooting at a target blindfolded and being told only that you hit or missed rather than that you are aiming high or low.
"My two cents aren't worth a dime.";