Q:

How would one use punctuation to indicate tone changes?

I'm imagining this sort of statement:

He's a... different... sort of person, I suppose.

Some people would pronounce 'different' in that sentence as though it was followed by a question mark, but not the rest of the sentence. However, writing it like this strikes me as wrong:

He's a... different? Sort of person, I suppose.

The second sentence doesn't look grammatically correct to me. That being the case, how would I indicate the change in tone accurately in writing?

A:

I think the ellipses are fine, but I agree with the comment from  the original site that italics would work as well.  But neither one really shows a question, to my reading.
If you mean for someone to be emphasizing 'different', I'd use italics.

"He's a different sort of person. Not like the others at all."

If you mean for someone to be using 'different' as a sort of code for 'strange' or 'unappealing', I'd use quotation marks.

"He's a 'different' sort of person.  Not our sort at all."

If you mean for someone to be struggling for words, I'd use ellipses.

"He's a... a different sort of person. I think that's what I'd call
  him."

If you mean for someone to be questioning whether he's really different, I'd use a question mark.

"He's a different sort of person? Is that what you're saying?"

If you mean for someone to be focusing in on the word different, while still asking a question, I'd combine things!

"He's a different sort of person?  Is that the word you'd use?"

Are there other possibilities?  Probably!  

A:

I love the "different? Sort of person" tonally.  The word different and the question mark really communicate that the speaker is STRONGLY questioning their own description as if they are still trying to decide.  Also the question mark after different makes the word go up in tonal pitch.  To my ears, no other punctuation achieves this.  The question mark also stops the phrase longer than other suggestions.  It's not correct but certainly creates a different sound in my head and thus a difference in the speaker's presentation.  I have a "test" posse of people that read my work and if they grasp my intent for the character, I use it.  Just sayin!  I Like It. 

A:

Personally, I wouldn't use punctuation to indicate the tone change at all.  Punctuation marks are like modifiers - use them too often and they loose their effect.  This is commonly acknowledged with the exclamation point especially, but holds true for many and perhaps all punctuation marks, with the possible exception of the period and quote marks during dialog.
If I wanted to convey a change in tone, I would actually describe the tone I was after or use descriptions of gestures or facial features to explain it.

"Well he's a," she paused for a moment, her mouth working silently as she racked her brain for the right word, "well just a different sort of person, I suppose."  She made air quotes with her free left hand when she said "different."

All standard punctuation, but the text itself should help explain the tone and meaning.
If you must use punctuation rather than words, Kate has provided a variety of useful suggestions.

