Character codes 128 to 159 (U+0080 to U+009F) are not allowed in HTML;
even if they were, they would likely be unprintable control characters.
Tidy assumed you wanted to refer to a character with the same byte value in the
specified encoding and replaced that reference with the Unicode equivalent.

##</code><code>##

$ perl -nle 'print if /\P{ASCII}/' inputfile | uniquote -vE cp1252
$ perl -nle 'print if /\P{ASCII}/' inputfile | uniquote -vE latin1
$ perl -nle 'print if /\P{ASCII}/' inputfile | uniquote -vE macroman

##</code><code>##

$ perl  -wle 'binmode(STDOUT, "encoding(cp1252)")||die; print "He said, \x{201C}I\x{2019}m r\x{E9}served.\x{201D}"' > sample

$ uniquote -vE latin1 sample
He said, \N{SET TRANSMIT STATE}I\N{PRIVATE USE TWO}m r\N{LATIN SMALL LETTER E WITH ACUTE}served.\N{CANCEL CHARACTER}

$ uniquote -vE cp1252 sample
He said, \N{LEFT DOUBLE QUOTATION MARK}I\N{RIGHT SINGLE QUOTATION MARK}m r\N{LATIN SMALL LETTER E WITH ACUTE}served.\N{RIGHT DOUBLE QUOTATION MARK}

$ uniquote -vE  macroman sample
He said, \N{LATIN SMALL LETTER I WITH GRAVE}I\N{LATIN SMALL LETTER I WITH ACUTE}m r\N{LATIN CAPITAL LETTER E WITH GRAVE}served.\N{LATIN SMALL LETTER I WITH CIRCUMFLEX}

##</code><code>##

$ perl -wle 'binmode(STDOUT, "encoding(cp1252)")||die; print "He said, \x{201C}I\x{2019}m r\x{E9}served.\x{201D}"' | uniquote --encoding cp1252
He said, \N{U+201C}I\N{U+2019}m r\N{U+E9}served.\N{U+201D}