It can be many Zero-Width Space, or a few Hair-Width Space.

You never know, when you don’t know CSS and try to align your pixels with spaces. Some programers should start a trend where 1 tab = 3 hairline-width spaces (smaller than 1 char width).

Next up: The <half-br/> tag.

You laugh but my typewriter could do half-br 40 years ago. Was used for typing super/subscript.

Maybe it isn't a space, but a list of invisible Unicode chars...

It could also be a byte length of a 3 byte UTF-8 BOM and then some stupid space character like f09d85b3

It’s U+0020, a standard space character.

I did exactly the same, thinking that maybe it was invisible unicode characters or something I didn't know about.

Unintentional click-bait.