This is not related to some CSS or font size; it's an issue with a font on your Ubuntu.
I see all just fine:
Also, I see the additional whitespace where you typed
(웃 ) in your question, which on your computer apparently was needed to fix the erroneous font, even in a regular paragraph?
If you figure out which font is used for those characters, try to disable it and see if the browser then uses another font that does a better job.
To determine which font is used, see How can I determine what font a browser is actually using to render some text? And beware that different browsers might use different fonts on the very same machine, like described there too.
(FileFormat.info claims that "U+C6C3 is not a valid unicode character". I don't know what that means.)