Does it work with emoji and accented letters?
Yes. Characters are reversed as you see them, so emoji, flags and letters with accents stay intact instead of turning into broken symbols.
What is the difference between the three modes?
Characters flips each line letter by letter (“abc” becomes “cba”). Words keeps each word intact but reverses their order on each line. Lines keeps every line as it is but reverses the order of the lines.
Can I use it to check for palindromes?
Yes. Reverse the characters and compare. For phrases, you may want to remove spaces and punctuation and use the same case first.