Salmon

 Salmon  is a 2010-era feed-based protocol part of the OStatus stack for sending comment notifications and has been superseded by the use of webmention, h-entry, and in-reply-to building blocks in the IndieWeb space.

IndieWeb Examples
There are no known examples of indieweb sites supporting or using the Salmon Protocol.

Bridgy Fed makes use of Salmon as it provides a bridge with sites that leverage OStatus as a means of communication.

However, most IndieWeb sites use webmention protocol to send notifications about comments to content on other sites.

Statusnet
In the past, StatusNet supported Salmon at least somewhat, as it was part of the OStatus stack supported by StatusNet.

Too Difficult To Implement

 * undefined personally I tried to read and understand all the pieces necessary for Salmon back in 2010 and it seemed like far too much work so I refocused on implementing smaller, more incremental building blocks that gave me immediate results on my own site.
 * tried to implement salmon to integrate with StatusNet in 2012 but eventually gave up due to complexity and lack of community support: "Now I have my improved indieweb site on my identity domain, I want to have a crack at getting salmon working. First for mentions/replies, then for private messaging. I *could* test the entire process on my own, but it'll be much more fun to actually exchange messages with another site. I can test with StatusNet for webfinger-enabled discovery, any volunteers to help test HTML based discovery?" http://indiewebcamp.com/irc/2012-09-27/line/1348769830000"I tried to implement salmon integration with statusnet but never got it working, with zero help forthcoming from the statusnet/ostatus community or codebase"http://indiewebcamp.com/irc/2014-08-26/line/1409060063416