I think it is a good idea to always use a space and the & in the snippet calls:
[!Wayfinder? &startId=`0` &hereClass=`current` &selfClass=`active` &level=`3` &outerClass=`topnav`!]
I know what you mean by the tutorials and even some of the documentation leaving out the witespace, but I think it is not a good practice.
If you want to twist your brain look at examples in the ListIndexer documentation:
[[ListIndexer?LIn_dir=ASC&LIn_sortBy=menuindex]]
No whitespace and no backticks? Will this work like this? I think that some of these may be old examples in the days before these things made a difference.