At the date of writing this Discord Nitro Scams are taking over Discord, all accounts are getting hacked and those hacked accounts send these scam advertisement to Friends list and Discord Servers. The Desperate Discord users who really want nitro are falling for these scams.
How do I identify scams?
You can check Discord's Twitter, if they haven't posted anything about the "promotion" then it would most likely be a scam.
Check if it's a Discord's Official domain.
See if the user sending the messages have nitro.
See if they respond after you message them after the advertisement.
Consult the other users and Discord's Community Servers.