Disappearing discussion threads?
I can no longer get to the discussion thread at https://www.duolingo.com/comment/655545, although 24 minutes ago someone posted a reply to one of my comments. Has the thread been lost?
Sometimes, if a spammer posts on a thread the thread may be disassembled or locked. If the post is spam then the whole conversation will be taken down. This may be what happened to you.
If the notification of their reply is still available under your little bell thing, just click their name and scroll through their profile. The discussion thread is deleted, but the record of their comment in it is not.