add comments

textattack/shared/utils/strings.py

@@ -33,7 +33,7 @@ def words_from_text(s, words_to_ignore=[]):
         if c.isalnum():
             word += c
         elif c in "'-_*@" and len(word) > 0:
-            # Allow apostrophes and hyphens as long as they don't begin the
+            # Allow apostrophes, hyphens, underscores, asterisks and at signs as long as they don't begin the
             # word.
             word += c
         elif word: