The cm-hr line decoration that draws the rule was applied unconditionally, so placing the cursor on a horizontal rule showed both the rule and the raw "---". Only style the line (and hide its glyphs) when the cursor is on a different line; on the rule's own line, emit nothing so the raw "---" shows for editing — matching how headings/blockquotes reveal their markers. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>