Is it academic misconduct to post assignment solutions on public websites?
I became curious that whether posting solutions to assignments of courses comes under academic misconduct or dishonesty ?


Generally, I would say that putting material online is not academic misconduct or dishonest. What is important in the question that you have linked is that the "dishonest" part for the student is not that he wanted to take material from the web (this may or may not be against the rules, but it is by itself not dishonest), but that he intended to pretend that he solved the assignments independently. Strictly speaking, I see it not as your responsibility to make sure that students that later on take inspiration from (or outright copy) your solution declare that they did so.

Of course, from a practical point of view, your behaviour may still be somewhat unpopular with your professors, as it clearly opens up additional venues for cheating for the next batches of students. Personally, as a lecturer, I was never bothered, because I strongly believe that you always need to assume that the solutions to an assignment that you "recycle" from the previous year are "out there" in one way or another. However, I know that other lecturers feel differently, so if you want to piss nobody off, you should check with the professors beforehand. In any way you should make sure that you are not uploading material that you do not possess the copyright for (for instance, lecture material or assignment descriptions).