Select quotes instead of quoted text

[AllanLRH]

In the following, suppose that a | is a caret, and foo [bar] baz a string where foo is selected.

Syntax: JSON, Sublime Text 3
"foo bar"
Activate select_quoted (I'd just put a --> from now on)
"[foo bar]"
Which is what I'd expect to happen. However, if I use this is not:
"foo bar|" --> "foo bar["]
"|foo bar" --> ["]foo bar"

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Also, if I set the syntax to Plain Text, the plugin doesn't work:

"foo |bar" --> "foo bar"
'foo |bar' --> 'foo bar'

The console outputs:

Info: scope 'text.plain ', score (0, 0)

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Calling the plugin many times in a row even managed to hang ST3 – suspect it might relate to the Plain Text problem above.