added comments

src/services/formatting/formattingScanner.ts

@@ -146,6 +146,10 @@ module ts.formatting {
             if (lastTokenInfo && expectedScanAction === lastScanAction) {
                 // readTokenInfo was called before with the same expected scan action.
                 // No need to re-scan text, return existing 'lastTokenInfo'
+                // it is ok to call fixTokenKind here since it does not affect
+                // what portion of text is consumed. In opposize rescanning can change it,
+                // i.e. for '>=' when originally scanner eats just one character
+                // and rescanning forces it to consume more.
                 return fixTokenKind(lastTokenInfo, n);
             }