This one is a bit obscure and easy to work around in source, but the inkcpp behaviour is different to native ink:

   ~temp test = true
    Glue <> 
		{
        - test: with
        } <> {
        - test: no
        } <> gaps.
	->DONE

Should produce Glue with no gaps., but inkcpp produces Glue with nogaps.. In native, this only works with } <> { on one line, if you split that up then native doesn't produce a gap either.

Low priority given how easy it is to work around.