Board Thread:Support Requests - Designing Your Wiki/@comment-35591859-20180406160452/@comment-9605025-20180408202333

I see now; thanks for that clarification. I have never used that method for preformatted text before since I don't usually use VisualEditor. However, it appears that the preformatted text, as used by VisualEditor, has two different methods in source editor. The first method is to put a space at the beginning of the line. I determined this by simply using the source editor to edit the page you linked to. The second method is to directly insert the HTML  tag. I determined this by using my browser's developer tools to view the HTML received from the server.

Using an extra space: Hello There

Produces: Hello There

Using the  tag: Hello There

Produces: Hello There

Getting back to your question, I believe the following should do the trick. You should put it on MediaWiki:Common.css.