I think this is a relative no-brainer. From soul sand on On The Hunt to glass (??) on Spaced Out, blocks that cannot be broken should not be able to be placed. I think optimally nodrop blocks should also be noplace, but there are some cases where nodrop is relatively liberally applied, and so the best solution would probably be to come up with a conspicuous warning if you're placing lapis blocks on Waterpit expecting them to be droppable after mining, etc.