The theme solarizedl has a small misfeature, namely the foreground color used for matching parentheses, used when the cursor lies in the vicinity of one of them, is nearly indistinguishable from the default background. Please see the following scaled screenshot

taken from a 250% scaled browser window and further magnified by xmag — I say this because at normal scaling, with the help of anti-aliasing, the invisible-ness is much more severe...

I have had a look to solarizedl.css and it seems that the culprit is

div.CodeMirror span.CodeMirror-matchingbracket {
 color: #ffffff;
 font-weight: bold;
 background-color: #fdf6e3;
}

but I cannot tell where in solarized.less the clause above is generated, so I cannot propose a patch.

PS wrt matching parentheses, I checked all the other themes and they are OK, the matching parentheses are always correctly highlighted.