There has always been some confusion about Rahne's name. Most of us have misspelled it. Some of us don't know how to pronounce it. Well finally, here is the last word on Rahne's name.
Rahne is pronounced like "rain," as in the liquid that falls from the sky. Not like Ronnie or Renee or anything else. This was confirmed in an editor's response in Report Card, the letters page of the original New Mutants comic. No other proof is needed, but there is an abundance of it. Also, Havok once asked Polaris what she thought of Rahne, to which she replied, "It makes the grass grow." Lastly, in X-Factor #87, Rahne dreams of Rahne's World, Rain Man and Rahne and Simpy. The puns don't work if her name is pronounced any other way.
If this is not enough to persuade you, Google "rahne" + "pronounced like" and see how many results you get.
So why is it spelled that way? No other English word spelled with an a-h sounds like a long A. But remember, Rahne is Scots. Her name must be pronounced the same way it would be pronounced in her home country. Even if Kitty got it wrong in an episode of X-Men: Evolution once (Retreat was the name of the episode, for you fanatics).
And remember, it's r-A-H-n-e, not r-H-A-n-e. The RAH at the front makes us think it must be pronounced like Ronnie, but that is incorrect. Another reason for the confusion is that there is a name spelled r-h-a-n-e and can be pronounced several different ways. However, it is masculine and Irish, and Rahne is neither. Just pretend that the H is an I and you will never spell (or pronounce) Rahne improperly again.
Sinclair is a surname, or clan name as it is called in Scotland, with a rich history dating back over a thousand years. Many families with various names belong to the clan. It is assumed that Rahne inherited the Sinclair name from her mother, whom she never met. Appropriately for Rahne, the Sinclair motto is "Commit Thy Work To God."