Niels,
My point of view is that the approved style is defined in the way that clang-format version 8 applied the settings defined in the ITK/.clang-format. If clang-format version 8 has a bug in it, then that bug becomes part of the style.
The emphasis is that an automation to keep the code clean and consistent takes precidence over a long list of manually enforced rules. Automation is key.
This seems to be an anomaly in the formatting with most of the code NOT having a space. I suppose you could use https://stackoverflow.com/a/25642688
// clang-format off
...
// clang-format on
to fix this clang-format anomaly.