It is Acceptable
Stack Exchange has two different kinds of forums. It has Worldbuilding, where the expectation is that queries will be somewhat opinion based and responses will vary wildly in subject matter and presentation. And then there is the rest of SE.
My take on the coveted Green Check Mark is that it is really a kind of "reward". Well done, good and faithful respondent! It doesn't mean what it means across the rest of SE. If I ask a question about balancing a chemical equation over on Chemistry, it's really only got one correct answer. I as querent can choose which of the three correct responses I award "accepted", but that doesn't invalidate the correctness of the other two.
Here in WB, it's often the case that one answer will be awarded the Green Check Mark, while another answer or more will be highly voted by the community. Over on Chemistry, this should never happen. In forums where "one correct answer" is the expectation, that's the one that should also be accepted. But here you can receive multiple correct answers. Each one is valid and the community may like one or more of the answers that you personally don't quite jive with!
My encouragement: On the negative side, the Green Check Mark is also a signal that communicates the message "Thank you for all your help! I don't need any more answers! I as querent consider the matter closed!" This is very much offputting for potential respondents.
I almost always pass over queries with accepted answers, even if I've got what I think is a brilliant answer that is different from the accepted. Why should I expend creative energy here when the querent is signalling an unwillingness to consider my effort? I've read comments to the same effect by other folks as well.
I'd actually encourage the practice of not accepting an answer at all. Just leave the question open! You never know what kind of answer you'll get a year from now or even ten years from now!
But if you do wish to honour a respondent with the Green Check Mark, I'd encourage you to wait a month. Yeah! A whole two fortnights! This will give some time for the question to drop away from immediate community awareness and for most folks to be alerted to its existence so they can answer if they want to.