Should DOM splitText and normalise compose to give the identity?

I was on the DOM Working Group in the early days; I'm sure we meant for textNode to contain the new joined value, but if we didn't say it in the spec, it's possible that some implementation might create a new node instead of reusing textNode, though that would require more work for the implementors.

When in doubt, program defensively.

While it would seem like a reasonable assumption, I agree that it is not explicityly made clear in the specification. All I can add is that the way I read it, one of either textNode or it's new sibling (i.e. return value from splitText) would contain the new joined value - the statement specifies that all nodes in the sub-tree are put in normal form, not that the sub-tree is normalised to a new structure. I guess the only safe thing is to keep a reference to the parent before normalising.

I think all bets are off here; I certainly wouldn't depend on any given behaviour. The only safe thing to do is to get the node from its parent again.