Ok, I understand Opera's Presto isn't supported anymore, but it's still a good browser. The issue is very simple. On the right top corner of repository overview page you have Page Controls. At the Opera 12 browser you see Share link is aligned to the baseline while all controls are aligned to the top.
Actually the reason and solution is clear. You have #repo-share-link have which have vertical-align: baseline; from .aui-button class. Meanwhile for other controls top align is specified or inherited from parent .aui-group > .aui-item class. So the solution is to add vertical-align: top; to the #repo-share-link selector.