In Libre Office Version of LT, if you check your text for correctness with F7:
If there is a blank followed by a line-feed (not a paragraph sign) it will be recognized as repeating blanks. If you type ‘ignore’ (‘Einmal ignorieren’) another line-feed is inserted. If you type ‘change’ (‘Ändern’) nothing happened at all.
I’m working with the German edition of Libre Office, so I’ll searched in the German grammar.xml for that rule, but I didn’t find anything.
It’s not in the grammar.xml, it’s probably MultipleWhitespaceRule.java from here. I don’t have time now to reproduce or debug the issue, though.