Why does the appenddictionaryvalue statement have a separator as a parameter?

Why does the appenddictionaryvalue statement have, as a parameter, “the separator for new value (or “” if no separator should be used)”?

No other dictionary stat/func has a separator. What purpose does it serve?

OK, I worked it out.

It’s not very well described – it took me a moment to work it out as well!

I’ve re-written it.