It might be Primal? 
Discussion
Here's a nos.social account with the double hashtags.
I'm not sure what this is all about… but I am only seeing one hashtag on my end? I posted this photo via nostr build - maybe that has something to do with it? I use Primal or Nos depending on my mood
It's nothing you've done, but something a client is doing. 
Do you remember which client you used to post this note?