01-12-2012
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Join Date: Aug 2005
Last Activity: 7 July 2020, 11:47 AM EDT
Location: Saskatchewan
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Just pasting the invalid characters into your web browser doesn't tell us what they are, as they will have passed through many levels of translation which have garbled them beyond recognition.
Conversion can't fix them if they're actually invalid in the first place, either. It'll find the "right" equivalent, if possible, for it to remain "broken" the same way in the different character set.
Can you show us part of a hex dump of the text file so we can see what the offending characters are? hexdump -C file