I once told an op how to solve, on a thread where Dave must have put hours of work in to help. The op then went and marked my quick bite of info as the solution!
I felt guilty as hell, and asked the op to remove it and put it on Daves, they did and all was well.
Obviously in that case, the solution was not by me. However, an op can mark any post they feel most likely as the solution. Whether or not we all agree about the solution is another matter, and of course it could be put in the wrong place by mistake. Thus, confusing future readers on a clear solution to the problem.
You could ask the op if they feel they've made a mistake. If they haven't, I'd just be happy to have helped.