There seem to be some locales or styles that use asymmetric spacing. From the Zen of Python—note different spacing based on context and position within the sent

There seem to be some locales or styles that use asymmetric spacing. From the Zen of Python—note different spacing based on context and position within the sentence: There should be one-- and preferably only one --obvious way to do it. Although that way may not be obvious at first unless you're Dutch. [...] Namespaces are one honking great idea -- let's do more of those!