The space would be rendered, turning the entire paragraph into <pre> (monospace text).

Similar issue: T46478

I meant rendered on screen, rather than rendered in wikitext. The entire block "<nowiki> </nowiki>" can (and should?) be omitted altogether; the user certainly didn't intend to start the line with an invisible space character.

In T90533#1069372, @Martijn_Hoekstra wrote:

I meant rendered on screen, rather than rendered in wikitext. The entire block "<nowiki> </nowiki>" can (and should?) be omitted altogether; the user certainly didn't intend to start the line with an invisible space character.

OK, merging into T68628: Spaces at the start of a paragraph aren't very obvious.