Intersect Tool Missing! Available as separate plugin.

[Dimitri]

'I'd consider the better / more correct result being the one where just the lines of intersection (as with Union result) are hard.'

Exactly, Paul... the hard edges are needed only in the 'seam' (or 'intersect') edges. The other ones are useless and trouble producing... to select them and turning them to soft ones is a needless tiresome process (Mark, I do wonder how did you conceive such a thing)...

'I see the use of hard edges as a temporary / interim measure - to maintain the geometry created by using booleans - whilst a better way (bevelling the seam / join) is implemented ... in D's case, by retopo approaches to re-establish proper eloops / geometry'

Just so... : - )