Given a population of 310,000 and a sample size of 230 you would have 95% confidence that 91% +/- 7% of your userbase is in support of shutting down the subredd

Given a population of 310,000 and a sample size of 230 you would have 95% confidence that 91% +/- 7% of your userbase is in support of shutting down the subreddit with your numbers. So yes, you can draw a conclusion of support from that. This is how polling works.