When using the US-International keyboard layout, if you want to enclose selected text with quotes, single quotes or back-quotes by typing them, the originally selected text is deleted.

Those keys are used for diacritical accents by the US-International layout and require two keystrokes, the quote character itself followed by either a space to indicate you actually want the quote character itself, or a different character if you want to apply the diacritical accent on it. For instance a single quote ' followed by an a gives á. If the quote character is followed by a character that doesn't accept diacritical accents then the layout issues the two characters as they were typed, so a " followed by a w gives "w

I do most of my programming using the standard US layout but sometimes I need to switch to spanish or french.