Apparently, multiple colons are simply ignored when executing Ex commands. For example,
:set number!
:::set number!
: : :set number!
all toggle line numbers. Is this really a consolidated rule? Where is it documentated?
I tried :helpgrep ::
and :help ::
but did not find anything relevant.
I came to this question after many times having copied Ex commands such as :set number!
and pasted to Vim's command line with :CTRL+R*, so that
the resulting command line had a double colon.