Long tem edit comments for logged in users

I have set up a private blog for myself and four friends – we all have full edit status but I am the only administrator.
Only we can enter posts, it’s not for the public.
It’s for personal projects so we can discuss and help each other.

But we are unable to edit comments.
There is no button visible or any tick box in admin section for a comment that I may have left on my friend’s post.

I can’t get ‘simple comment editor’ to work either, though that seems to be for non-logged in users.

What I want is long term editing on anything we have personally added –
we are mature adults so want to be able to edit our comments at any time (even time limited would be better than zero ability).

How would I do this?

Theme is Pixel 1.9.8
Worpdress is v 3.1

FYI: I’m a PHP expert .. but not a WP expert