how can it damage your lens ??
think about it

a laser does one thing and one thing alone
it sends out light to the cd and the reflected data gets read and thats that
now if your reader cannot read a cd properly because its a cdr or cdrw then itll retry reading that particular sector and after a few attempts it will just quit reading the cd.

now there are people damaging there lenses and stuff by modifying there dc's laser to a higher output to get it to read cdrw and thats propably what you heard about