In my opinion, it is useful to all researchers if we include any alternate spelling that we have encountered or that other researchers indicate to us may be the "correct" spelling. I believe that the Other Nicknames and Other Last Names fields style guidelines basically cover this concept.
Sometimes a researcher presumes the spelling if he/she only has heard the name, rather than having encountered it in a document.
For example, I always thought my grandfather's brother's name was Arlen or Arland, because that's how my mother pronounced it. One day, I asked her to spell the name and discovered it was Ireland!
The more information we provide, the easier it can be to find source documentation. Including alternate spellings in simply another basic research tool.