This is an unmodified Nova style installation. The default prefix is unreadable when moused over. You can see an example of this on the homepage of https://www.grummantalk.com currently. The problem does NOT exist in the forum view (https://www.grummantalk.com/forums/grumman-aa-5-series.8/). It appears to only happen on the homepage, and when selecting a prefix during thread creation.