I suggest to add information to the pop-up window that appears when moving the mouse over a member's avatar to show the ratio of posted and unanswered questions in the context of the current forum space. Below is an example of an avatar. There would be enough room to add another row to display such statistical information, for example: "Unanswered questions in current forum space: 10 %".
This information will be very helpful for everyone to spot users who do not follow-up or respond to questions, or who do not mark their questions as answered. As a result, these members may not receive answers until they improve their behavior, and to my experience, most of the people get the message.
I also think this would have a positive influence to reduce the number of unanswered or abandoned questions and might be a better motivation for people to mark helpful and correct answers than the gamification and notification options that currently exist.