Problem
In a web application dealing with products and orders, I want to maintain information and relationships between former employees (users) and
Your idea does make sense and is used frequently in production but, to implement it you will need to update quite a bit of code to account for the new field. Another option could be to archive (move) the "soft-deleted" records to a separate table or database. This is done frequently as well and makes the issue one of maintenance rather than (re)programming. (You could have a table trigger react to the delete to archive the deleted record.)
I would do the archiving to avoid a major update to production code. But if you want to use deleted-flag field, use it as a timestamp to give you additional useful info beyond a boolean. (Null = not deleted.) You might also want to add a DeletedBy field to track the user responsible for deleting the record. Using two fields gives you a lot of info tells you who deleted what and when. (The two extra field solution is also something that can be done in an archive table/database.)