I generally remove information from entries if that information is already available (especially in more detail) in another entry. In the case of ablaut, the etymology of the words ab or Laut isn't really relevant. If someone is interested in that, they would presumably look up those words.
I am not trying to argue for arguments sake, but it seems like we should be adding to not deleting from the entries. I understand if it is so confusing that no-one in their right mind could understand it, or if it was so obscure that it would never be used, but the information removed is "once-removed" (pardon the pun) and I feel relevant. I don't know. Speednat (talk) 17:27, 4 January 2013 (UTC)