diff --git a/lib/rules_inline/state_inline.mjs b/lib/rules_inline/state_inline.mjs
index 8d33819..35d77d5 100644
--- a/lib/rules_inline/state_inline.mjs
+++ b/lib/rules_inline/state_inline.mjs
@@ -119,10 +119,11 @@ StateInline.prototype.scanDelims = function (start, canSplitWord) {
     // treat beginning of the line as a whitespace
     if (pos <= 0) { return 0x20 }
     const charCode = str.charCodeAt(pos - 1)
-    // not low surrogates (BMP)
+    // not a low-surrogate code unit (is BMP code point)
     if ((charCode & 0xFC00) !== 0xDC00) { return charCode }
 
-    // undefined if out of range (leading stray low surrogates)
+    // undefined if out of range (typically due to isolated low-surrogate code unit
+    // at the beginning of the string)
     const codePoint = str.codePointAt(pos - 2)
     // undefined > 0xffff = false, so we don't need extra check here
     return codePoint > 0xffff ? codePoint : charCode