The new and otherwise absolutely awesome Opera has been having font drawing issues ever since version 15. Based on small testing it seems that the problem randomly occurs when the font is defined as Helvetica, or "sans serif".
At first I thought it was a problem on my end, as I'm using Font Explorer to manage my fonts (as most designers working with fonts do/should do), but am not so convinced of it any more because:
a) Opera's the first time in 5 years I've encountered this kind of a problem;
b) the behaviour seems to be pretty erratic in Opera as well. For example, when I open the same Wikipedia front page in a new window, it displays just as it should:
But at the same time, Github remains broken even in the new window.
Opera's Discover page menus (topic selection and country selection) used to have the same problem in O15, but they display correctly now.
I doesn't seem to be a common issue as it's still existing in O17, but needing to open Safari all the time to just be able to read some sites is getting stale...