Bug introduced in 12.3 or earlier and persists through V13.0.1
I'm using Mathematica 12.3.1 on Windows. Most or not all pages do not show the Underscore character with Patterns. Is this only on my laptop?
e.g. Documentation ref/DirectedEdge
or ref/Cases
When I copy and paste in another Notebook I see the Underscores. @Michael-Mccain and @ Rob-F commented that Magnification plays a role here and it does indeed. I'll report it to Wolfram Support The Underscore is only invisible in Documentation notebooks with Magnification at 100%. Above or below 100% magnification show the underscore.
UPDATE: With magnitude at 100% and resizing the window up to left until the cell contents needs to be repositioned (e.g. the text is to long for the window to fit anymore and then the frontend shows the text on multiple lines)
so here it's not there:
but here it is (at 100%)