Well I think it is fair enough if they are like myself and my wife. We make it quite clear that it is wifes pictures, but I do 90% of the posting, always with her knowledge and most of the time while she is with me at the time. I would say this would be pretty similar to most in here.
I would think that quite a few would be like my wife and I that we read the comments together but we make it clear in our reply who is doing the writing.
Personally, it is husband in the forum 100% of the time but maybe 50/50 who replies to comments or PMs.
If they specifically ask for my wife to reply, then I will let her do it, but her written English is not great, so often I help, with her alongside.