Just a quick note that I have submitted a patch
<https://gerrit.wikimedia.org/r/190819> that will make MediaWiki avoid
serving SVG images to Opera 12 (the old, Presto-based one) when a PNG
fallback is available.
We support it as a Grade A browser, which means that we should do our best
to provide the best possible experience. In my opinion, the best possible
experience involves not giving it any SVGs.
Opera 12 has issues when rendering SVG background-images together with
border-radius or background-size rules (see task
<https://phabricator.wikimedia.org/T87504> for details and examples), and
both of these are becoming increasingly common in our codebase. One common
complaint was the new MediaWiki UI checkboxes, where the check icon would
sometimes not appear for Opera users.
--
Bartosz Dziewoński