The usage of percentage sign is a little contentious around the world, with some adding a space between the number and symbol and others not.
Modern US English overwhelmingly uses no space between number and symbol and other English-speaking countries also generally prefer no space. In other languages there can be a lot of variation including "x%", "x %", and "%x" so it might be nice to one day add a preference.
However, we do not use it consistently. We use x% everywhere except when using percent as factor (Preferences / Interface / Editors / "Factor Display Type". You will see the different formatting used simultaneously in the image below:
This patch changes "percent factor" to use the same convention as elsewhere, to not have a space between number and symbol.