I suspect the problem here is related to
CHARSET or the symbol set option on the
FONT specification.
I think you need CHARSET=LATIN1, and to specify the ANSI option for the symbol set with your font in order to display 'smart' or 'curly' quotes in non-GUI mode. Without LATIN1, you're basically in 7 bit mode. And although both OEM and ANSI symbol sets support most or all of the typical accented characters, the OEM set does not include some of the more exotic ones like the smart/curly quotes.
I vaguely recall that you guys didn't use CHARSET=LATIN1, which I thought was actually necessary for GUI click-string support (since the lead-in sequence uses an 8 bit character), but somehow it worked for you. Changing it at this point might affect the display of existing data though (assuming you have 8 bit characters stored in fields).
Unfortunately, there is no obvious way for INFLD in GUI mode to know whether the data you're inputting will ever be displayed in a more limited font/character set, so automatically filtering the input doesn't seem possible. But we could add a TYPE code to force it to convert common 8-bit characters to 7-bit approximate-equivalents. Although if you use your own INFLD wrapper, then perhaps adding the problem-character detection/conversion logic to it would make as much sense.
Let me know what you think.