To reverse that, in a way, at what point does penalising breaches of standards that do no harm become unacceptable?
I've got experience of this sort of thing from both sides - I once spent several frustrating weeks porting source code from a system with a lax compiler to one with one which rigorously stuck to the ANSI/FIPS standard.
Would my life have been easier had the original programmers not been allowed to write non-compliant code?
Yes.
Would my life have been easier if the compiler on the target system had been as lax as the one on the source?
Yes.
Did the non-compliant code work?
Yes.
So you have to ask, as I do, just what is the merit in insisting on standards adherence in situations where breaches do no harm?
As I observed, IE is happy with the URL with a space in.
Firefox is happy with the URL with a space in.
If you have Chrome, or Opera, or any other browsers available, I'd be interested to know what they make of it.
And I'd also be interested to know what non-pedantic reason there is for this site's forum software to not allow a URL with a space in it, when bracketed with [URL] tags to negate the parsing issue, to work.