I've mentioned before that I use Inoreader to manage all the RSS feeds that I follow. It may not be the flashiest service out there, but it packs a lot of power under the hood if you opt for a paid plan.
The other day, they announced a new feature that tackles something that I periodically have to deal with, duplicate posts. This comes on top of the existing abilities to filter feeds to remove posts you're not interested in, and makes my overall reading experience even smoother.
Another thing that I like about Inoreader is that they are genuinely concerned about providing a good service to their customers. The web dashboard can be customized to flag up feeds returning errors, as well as those that have been inactive for a long time. And their browser extensions make it easy to subscribe to new sites. They even have technology that can attempt to pull content from sites that, for whatever reason, don't have RSS feeds.
I cannot recommend them highly enough.