We're using `@extend` with a placeholder selector to generate the code
related to the icons. That means the generated CSS code will look
similar to:
```
.something,
.something-else,
.in-favor-against button:not(:hover, :active),
.etcetera,
.more-etcetera {
/* Rules here */
}
```
That means that, if one selector isn't supported by the browser, none of
the specified selectors will apply these rules.
The `:not(:hover, :active)` selector, introduced in commit 3482e6e05, is
currently supported by 96%-98% of the browsers. Browsers like Internet
Explorer don't support it.
Since there's a simple solution for this issue which results in a big
gain for 2%-4% of the population, we're fixing the issue by avoiding the
non-universally supported selector.
933a461f17