My personal opinion is that texts are easier to
read if words are relatively short. Having a few
additional spaces doesn't hinder quick reading,
I think.
So my personal advice would be: as many word separation
as possible!
Actually, an easy/quick reading does not necessarily result from simple separation of words, but rather from tactic separation of grammatical/semantical blocks
of which the text is made up. Indeed, there are languages where spaces are not as conventional as in the European languages and yet the speakers are capable of quick reading. Chinese speakers, for example, can generally perform skimming & scanning techniques better than English speakers, while there's hardly a space in the Chinese text.
There seem to be more people who do not put a space between {le} and {nu} than those who do. Probably because that's easier to read and grasp. Separation of words does not necessarily guarantee easiness in reading. Too many spaces between words in Lojban sometimes make the text inconveniently fragmented. The more I study Lojban, the more I find {.iseri'abo} facile and {.i se ri'a bo} disconcerting.
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