I had the same issue with Feedly's "features". I've maintained a stylish extension for Feedly that I keep adding to. Every time they add something that I don't want to see, I hide it via css. Thanks for the prompt, I just hid the patronising "Well done" that's been annoying me.
If anyone else wants to try to strip feedly back, they can try my css here: https://gist.github.com/wvl/4cd7d7d314fe9a544f2851296db61bb9