Question: Having read a style guide recently, I was under the impression that you don't add commas after the ellipsis when the ellipsis indications pauses or thoughts trailing off, followed by "he says" or the like.

E.g.

"If only I had known..." she whispered.
"If I'd known, I would have never..." he says, his voice going quiet.

However, I've recently seen several novels which stick a comma after the ellipsis.
E.g. 

"If only I had known...," she whispered.

"If I'd known, I would have never...," he says, his voice going quiet.

Does anyone have an opinion about which is correct?

I also have a question about spaces before the ellipsis. I see books with and without the space and have heard different opinions on the subject.

Is this correct:

"If only I had known..." 

Or should it have been:

"If only I had known ..." 

Thank you for any advice.

Answer: 
Punctuation is a matter of style, and you should be guided by your manual of style. There isn't any absolute right or wrong. I use *The Chicago Manual of Style*, which recommends using the comma to separate the speech from the speaker. It also recommends space (3-to-em) around each of the points used in *quoted* text, but the applies that typography to its examples of faltering speech.
It is a matter of personal preference. Nothing's written in stone. Styles change, and those who change them are called humans.

That said, an ellipsis immediately followed by a comma looks silly.