There’s no command to delete a record from a physical file from a CL program. You’ll need to create an RPG program or an SQL script.
It’s also not advisable to delete comment lines from source files – they’re normally there for a reason – to explain what a program is doing and why.
I once worked at a site where the manager had removed all the comments from all the program sources (he said that the programmers should be good enough to work without comments otherwise they shouldn’t be there!) – this made all the changes take much longer than they would have without the comments as you had to investigate what the program was doing before you could make any changes.
Having said that – bad, misleading or meaningless comments are worse than no comments at all.