With Understand 6.3 we added a new spellchecking feature to Understand. By default, it will check your comments for misspelled words and underline with a squiggle them to bring them to your attention.

From there you can right-click on the underlined word and find options to fix the spelling or add it to your custom dictionary.

A fun fact, we know the valid entity names in the file, so we consider those valid words as well, and they shouldn't get underlined. 

The default settings only check your comments for spelling, but if you're like some of us, you might also want to check the strings in your code. Nobody likes a customer pointing out their spelling mistakes.

You can enable this feature in Tools->Options (or on Mac under Preferences). Select Editor->Advanced and look for the Spellcheck section at the bottom.