@schajuli I feel like this should work, but I'll have to try it and see if I can reproduce the issue you're seeing.
The pidfile errors are probably because the files you copied over don't have the right permissions.
We're using NodeBB comment plugin that we added to our WordPress blog. When users start commenting, they get then notified for every single answer when they actually want to be notified only to their own reply.
Is there a plugin or a known hack to receive notification email to own reply only?
In user settings, uncheck "watch topics you reply to", and then you'll only get notifications if someone mentions you.