Using ASCII Symbols in Before:After CSS triggering Error 500 or 'disallowed characters' on save

ElMuggs

So I was trying to add some ASCII symbols for text-decorations via the :before and :after tag's but came across a bug/problem in that using the html/css code for symbols are not allowed, and certain symbols will trigger a error 500 on save.

For example this bit of code is 'technically wrong' but works fine all the same:

hr:after
{
    content: '⬥ ⯁ ⬥';
}

but using the proper CSS codes like the below:

h2.adventure-log-post-title:before
{
content: '      \00A7';
}

Gives get the error:

Custom css Invalid or disallowed characters in the CSS.

We do not allow Javascript or other advanced CSS, just the basics.

Which wouldn't be a problem except that that replacing the CSS code with the some symbols like the below will trigger a Error 500 on trying to save : 

hr:after
{
    content: '☙';
}

Would it be possible to consider allowing the CSS Entities list to be allowed for the ASCII character set to make it easier to do proper html/css - or if not is there a list of which ones are 'allowed' and which are 'banned?'.