Your title suggests Lemmy is proprietary which it is not.

Lemmy and KBin are both open source. [implying: "OP suggests Lemmy and/or KBin are not open source"]

*sigh* in no moment the OOP even implies that.

On-topic: PieFed is packed with a bunch of interesting stuff, mentioned by another user in that thread: better resource usage, better mod tools, gallery view, the ability to combine comments from different comms, a multi-reddit-like feature... and, additionally:

• a button to mute all replies to your comment
• an "attitude" score, to detect people who are excessively combative
• filter posts based on keywords

I'm actually rather excited for it, because it seems to be progressing at a fast pace.