Ha, I wouldn't have thought to criticize the spacing, but I did see one person complain as I explored old Nim discussions. Nim being strict on tabs is something I see as a good feature for the same reason the style flexibility made me instinctively flinch back. I've experienced mixed tabs and spaces in Python code and I do not like it; the flexibility leads to inconsistency.
The idea is to make it easier for projects using different conventions to be built on top of each other without making things harder to read - and in practice it actually works really well at that.
On the upside, people freaking out over the style insensitivity makes for a nice change from people freaking out over nim caring about whitespace, so at least we get some variety in our aesthetic worrying from people who've not had time to try the language yet :D