I never use the lever. The lever is an added safety, to eliminate someone from pulling the trigger with a round in the chamber. What did people do before they started installing the sear deactivation lever? They used common gun safety and insured there was no live round in the chamber, prior to pulling the trigger. I would hope those that use the lever would still check the chamber first, to make sure there is no ammo loaded. But if you use proper gun safety and check that you weapon does not have a round in the chamber (along with no loaded magazine), then there would never be an issue by pulling the trigger, instead of using the sear deactivation lever. I also do not put my car in reverse and start backing, without looking rearward first, but I am sure there are some that do. Safeties are added to prevent accidents, which in most cases would be prevented if proper gun safety is followed. Name a safety that is necessary. Even the "drop safety" is not necessary, if you insure that you never drop your gun. However with the nature of us human beings, we do need extra help to prevent accidents, and that is why those safeties have been added to the guns.

To the OP question. No you will not do any damage to the gun by not using the lever, whether removing or installing the slide.

Bob