Facebook – Editing a Facebook comment that was too long to post

No, it's not possible. The permissions for a post come all together by the relation this person has to you (group/friend/etc.) - if you can see it, you can comment on it.

The option to disallow comments is available only for groups via the relatively new feature Turn off comments (something like that) for individual posts.

You cannot change that no.

However, you can see what the privacy settings for that post are. Underneath every post in Facebook is a little icon, showing who can see that post. When you hover over it, it will tell you in more detail what the icon means. A globe means the post is Public (anyone can see it), 2 little persons mean only friends, the same 2 persons, but the right one in a lighter gray means friends except people who you added to the Acquaintances list, a padlock means only you, and a gear symbol means custom settings, which you can figure out by hovering over it.

If your friend has made his post Public, your friends could end up seeing it. If it is Custom, it is also possible they could see it, but it's not sure, unless it tells you when you hover over it. There used to be a Friends of Friends setting too, which also allowed your friends to see it, but that seems no longer available.