[sciurius]

Formally, ChordPro does not impose restrictions on what can be a chord name. Anything is valid, e.g.,

    [A Quick Fox]Jumps over the dog

However, if you want your favourite ChordPro processing tool to do something intelligent with your chord (e.g., print a diagram, or transpose) then you may find that the tools impose restrictions on what chord name are recognized. Generally accepted chord names are like Am and C#maj7#5. And in general spaces are not allowed. (Yes, there are exceptions.)

So even though it is not a formal restriction of the ChordPro format, it is best to stick to generally accepted chord names and not use spaces.

EDIT: Having said all that, I agree that [Bm add5] should completely render in chord style, just like [A cappella], [Coda], [Fine], etc..