I start from a .tex latex file that contains:
\lipsum[11] blahblah
I import this in LyX.
Then I export the .lyx file to plain latex (.tex) and I find this line:
\lipsum{[}11]
This seems to be due to the fact \lipsum command don't take arguments
but a unique optional argument (between square brackets). So LyX may
consider, as no '{' was found after \lipsum, that lipsum command
takes the next char as argument (the opening square bracket) and puts
it between accolades. Maybe there is a way to fix this a simple way?