Where did you get that screenshot?
I'm unsure FILTERS file is supposed to be markdown formatted.
But if yes (or we'd allow that):

• either it must get more fixes (there are several other tokens with a single backslash)
• I'd like to use enclose the code in `, so to have \s instead of \s either
• it must probably get <!-- vim: syntax=Markdown --> (like our ChangeLog) or renamed to FILTERS.md

Where did you get that screenshot? I'm unsure FILTERS file is supposed to be markdown formatted. But if yes (or we'd allow that):

• either it must get more fixes (there are several other tokens with a single backslash)
• I'd like to use enclose the code in , so to have \s` instead of \s either
• it must probably get <!-- vim: syntax=Markdown --> (like our ChangeLog) or renamed to FILTERS.md

I took the screenshot directly from https://fail2ban.readthedocs.io/en/latest/filters.html