You know, in SE markup language in the editor, a row of dashes is useful.  You can either make a headline by putting a row of dashes under a short line, or you can create a horizontal rule with a line of dashes separated by white space.  

When I try that in iOS 12, I get this

———

Or this 

Headline
———

Note that I have hit "dash" six times and gotten 3 dashes.   And it does not work.  No horizontal rule (all the way across). No headline.

The problem is, they're not real dashes from 7-bit ASCII.  They are some sort of typographical oddity - em space, en space, whatever.  I see I can also hold the dash key and it will give me the options for em space and en space.  None work.  

How do I tape a plain ASCII dash in iOS 12? 

I realize this is a bit of an XY, but I need plain dashes for lots of other things too.