Moderation of this subreddit

Yesterday a popular thread on this subreddit was locked without explanation: https://www.reddit.com/r/Gent/comments/1go3bo0/voor_gent_en_groen_bereiken_akkoord/

I looked for a comment from a moderator, then I looked for the subreddit rules and... nothing that indicates why this happened. One can speculate but it seems a little overreaching to just lock a thread with an active discussion. I know it's common in bigger reddits (where it is very common to lock or remove threads) but it seems very unnecessary here.

Does anyone have extra insights or experiences into how this sub is moderated?