If one is looking for all "answered" questions, it's harder to find without a prefix.
Create a prefix with your question, i.e. "Question", and when it's resolved, automatically mark the prefix as "Answered". This is the best approach, in my opinion. An extension of this (by a developer) could be a 3rd option where if no reply is made in X days, it can be prefixed to "Awaiting Answer"/"Unanswered"/etc. to give members an opportunity to address them as a prefix will stand out better.
While that does show that it's answered, it doesn't do a very good job at organizing answered, unanswered or awaiting answers without an automated prefix set to change "Q" to "A" when selected and "Q" to "Awaiting Answer" after X days. Prefixes can be easier to browse for solutions over the smaller checkmark (but thank you for pointing that out so I can see how it works).
This is how I believe it should be (main forum):
As of now, it's up to moderators to find answered/unanswered questions to mark them as such so they're easier to identify in even "What's New".
Yes, it does. But does "What's New" which shows prefixes that can be searched. I believe even "search forums" can include answered posts if you select that prefix too, but I haven't played with them that much...