One issue with deleting a DGC non-atomically is that deleting only the base character can lead to all sorts of strange and problematic combining character sequences. At a minimum, deleting a base character should delete the entire DGC atomically. In Hebrew, I don't see any problem with deleting combining characters non-atomically (although one might want to limit this to just off the logical end of the sequence out of user interface considerations). I suppose that this might be more of an issue in some other languages, though.
One might be tempted to use some sort of canonical ordering logic to keep the complexity down, but the combining classes for Hebrew are so problematic that this would be a lost cause. I have used software where the cursor moves non-atomically across a DGC in Hebrew and I find it extremely confusing. The only way to make sense of what's happening is to remember the exact sequence in which the combining characters were entered. If someone wants to support such movement anyway, I think that the cursor shape needs to change dramatically to indicate what's going on. This is something I've never seen done well (usually not at all). Subtle changes in cursor position are useless as a visual indication to the user of what's going on. One might even need to include some sort of glyph highlighting to make clear the state of the text entry system. Ted Ted Hopp, Ph.D. ZigZag, Inc. [EMAIL PROTECTED] +1-301-990-7453 newSLATE is your personal learning workspace ...on the web at http://www.newSLATE.com/