Continuing the discussion from The Society's Community "How To" Guides:
You have two options if you want to ignore a user:
1 - Just ignore them, job done.
2 - Let discourse help you and set them to be ignored in your preferences, as explained here:
Go to your own profile page by clicking your avatar in the top right corner and then clicking the rightmost icon on the top of the pop-up window. From the menu that appears click preferences.
On the next page, choose ‘User’ from the menu on the left.
On the next screen click ‘+Add…’, in the ignore user section.
In the popup window, start typing the username in the Username textbox, select the user as it comes up. Set the timeframe and click ‘Ignore’.
Job done (repeat if you want for other users), this will hide the messages, you can still unhide each message if you so wish.