I’ve refreshed Newsblur but I still don’t see anything in the global preferences menu (but I do see clustering in my feed, and I can see the per-feed clustering settings options).
For some reason, the only clusters I’ve seen so far have been dupes. E.g. here, before-click:
…and here, after-click:
I wondered if maybe this was because I had the feed stored in multiple folders and maybe it was treating each feed+folder combo as a different entity, but this particular feed (http://feeds.bbci.co.uk/news/world/rss.xml) is only in one folder so that’s not it