Allow a character to be rendered as a space even with spaces removed.
In languages like Khmer and Thai there are no spaces between words, but spaces are used between phrases, much like a comma. Having these spaces between phrases really makes the text more readable (imagine english with no commas). Maybe this could be implemented in other ways, but the most straightforward way seems to be to allow some other character to be rendered as a space. I tried using the existing substitution function, but it seems to process before spaces are removed. Maybe there could just be another substitution option after all other things have been processed.