Strange font behavior in Opera 12 - why?

Question

Opera

On the page www.digitalmediaminute.com/reference/entity/index.php (this is a cheat sheet on XHTML entities) I suddenly encountered this behavior:

I.e. When selected as Times New Roman, Comic Sans MS, or Georgia, some characters are "blurred".
In a pure html file, this behavior was repeated.
Uncommenting the first line fixes everything.

<!--<style type="text/css">div{font-family:Arial, Helvetica, sans-serif;}</style>-->
<div>&crarr;</div>
<div>&lArr;</div>
<div>&dArr;</div>
<div>&empty;</div>
<div>&notin;</div>
<div>&lowast;</div>
<div>&cong;</div>
<div>&nsub;</div>
<div>&oplus;</div>
<div>&otimes;</div>
<div>&sdot;</div>
<div>&weierp;</div>
<div>&image;</div>
<div>&real;</div>
<div>&alefsym;</div>
<div>&lceil;</div>
<div>&rceil;</div>
<div>&lfloor;</div>
<div>&rfloor;</div>
<div>&lang;</div>
<div>&rang;</div>

In Opera > 12 versions and other browsers, nothing like this has been noticed.
It would be interesting to know what is the reason.

Answer 1

It is necessary to add something like this.
Then everything should be fine. And don't listen to them, opera12 is a good browser.

Answer 2

Opera12 becomes ie6 on a local scale, there is no point in complaining, it is necessary to update.

Answer 3

the reason is poorly implemented anti-aliasing
forget about Opera 12