I always comment out a sig because I appreciate the fact that some of them are quite elaborate and people have gone to a lot of effort to make some of them. Commenting out saves them some time when they have to edit and it doesn't take any extra effort on my part to do so. However, if a sig is over the filesize limit I will just delete it without the commenting out part.
I do not say please when I edit sigs. After you have done so many edits (many times to the same member), it ends up being very routine and everyone gets a generic message from me as to the reason for the edit. I can understand new members not knowing the restrictions and some of them will get a PM from me with explanations. For these members I do say please. Other members who have been here for any length of time should know the limits and not be upset when they are reminded of them.