By default, FlatPress replaces some characters (or character combinations) within your entries and static pages:
- Two hyphens ("--") become an en dash ("–"), three an em dash ("—")
- Three dots become an ellipsis ("…")
- Quotations marks: "text" will become “test”
- Trademark sign: "Text (tm)" is being replaced with "Text ™"
- Multiplication sign: "2x3" is displayed as "2×3"
How to disable
If you would like FlatPress not to do these character replacements, just tell it to

After the first three lines of your index.php, just add the highlighted line:
<?php
include 'defaults.php';
include INCLUDES_DIR . 'includes.php';
include SMARTY_DIR . 'SmartyValidate.class.php';
remove_filter('the_content', 'wptexturize');
define('MOD_INDEX', 1);
...
More details
The described replacements take place in the function wptexturize() in fp-includes/core/core.wp-formatting.php. Please refer there for a detailled view into the replacement logic.