You can "force" the wrong font characters if you try to use a font that is not known to the fontregistry: Open a fresh image (40463) and execute the code:
|text font1 font2 string1 string2| font1:=(LogicalFont familyName:'Source Sans Pro' pointSize:20). font2:=(LogicalFont familyName:'Arial' pointSize:20). string1 := font1 realFont asString. string2 := font2 realFont asString. text := TxModel new. text at:text startPosition insert:(string1, String cr, string2). (text startPosition selectTo: text startPosition + string1 size) applyAttribute:(TxForeColorAttribute with: Color red); applyAttribute:(TxFontAttribute with:font1). ((text startPosition + 1 + string1 size) selectTo: text endPosition) applyAttribute:(TxForeColorAttribute with: Color blue); applyAttribute:(TxFontAttribute with:font2). TxTextEditorMorph openInWindowWithText:text. Or am I the only one ? This is, how it looks for me:
