Hi 
There are two options I see here. The first is that you post something and then transfer ownership of your post / topic to system. This can be done by going to the post admin wrench 
and selecting ‘Change Ownership’
The second option is to Impersonate system by going to https://your-site-name/admin/users/-1/system and scrolling down to the bottom until you see this
This will be next to the merge, delete and anonymise user buttons.
I believe that for this to work, your email must be in the developer email in the yml? (someone can correct me here if I’m wrong)
Hope this helped 