The sharing menu is populated by the system. It shows apps that accept the content being shared. So, long story short, you installed something called Plurk at some point...
OK. That's what I thought, but I don't see anything by that name on my phone, and it opens a browser. So I thought it was something you guys might have added in. I guess I'll have to do some further investigation on my phone then.
Comments
https://www.reddit.com/r/htc/comments/5jumz8/htc_m9_running_android_version_60_something/