What’s the usage of apostrophes in " ‘Bye, ‘bye "?

I’d like to know what effect an apostrophe has which is before a word and doesn’t work as an omitter. (Not like C’mon or ‘Course, but like ‘bye, ‘bye.)

I have three questions as follows, but any comments about this type of apostrophe are very welcome. My primary goal is to get its usage for future reading.

1. What effect does the apostrophized bye have in the following scene?

”Will you come and visit me in my bathroom again sometime?” Moaning Myrtle asked mournfully as Harry picked up the Invisibility Cloak.

”Er … I’ll try,” Harry said, though privately thinking the only way he’d be visiting Myrtle’s bathroom again was if every other toilet in the castle got blocked. “See you, Myrtle … thanks for your help.”

” ‘Bye, ‘bye, “ she said gloomily, and as Harry put on the Invisibility Cloak he saw her zoom back up the tap. (Harry Potter 4 [US Version]: p.466)[Bold font is mine]

N.B.: Moaning Myrtle, a ghost, loves Harry, but one-sided. She wants him to come to the bathroom where she lives whenever he can. She sees Harry for the first time in a long time.

2. How would you pronounce it?

3. Are there any other examples for this type of apostrophe?

Meaning/effect: In the passage you cited, 'bye actually features the apostrophe as an omitter -- instead of the full "goodbye", the author used the shortened form. 'Bye is a more informal way of bidding someone farewell. For a better discussion of the forms of goodbye, I would recommend this question :"Good bye", "Bye", "Bye bye".

The effect of this use, in the passage, is that Moaning Myrtle is being informal with Harry. She is sad that he is leaving, and her use of "'Bye, 'bye" reflects both her sadness and her level of comfort with Harry. Note that the phrase is not always sad. It can also be used in a "cutesy" way.

Pronunciation: 'Bye is pronounced like the second syllable of "goodbye". It also sounds the same as buy (at least in most dialects of English that I have heard).

Other examples: Since this apostrophe actually still serves as a sign that something was omitted, your examples of C'mon and 'Course still apply. Another good example is

'Scuse me!

This is short for "Excuse me!", but it is highly informal. In most instances I can think of, when an apostrophe stands for omitted letters, the resulting phrase is highly informal.