Hovering over an Australian flag gives you 'American Samoa', hovering over an Austrian flag gives you 'Australia', etc.

Where?

Tried a few pages, not seeing it.

e.g. here

yes I see this too...
on page https://www.boincstats.com/stats/-1/user/list/16/3400#3489
the page html code contains...
<img src="/image/flag/Australia.gif" alt="American Samoa" title="American Samoa">

should be
<img src="/image/flag/Australia.gif" alt="Australia" title="Australia">

Cheers
Paul

Can't confirm, a page like https://www.boincstats.com/stats/5/user/list/0/3700#3715 looks fine be me:

The other pages mentioned https://www.boincstats.com/stats/-1/user/list/0/200/#289 and https://www.boincstats.com/stats/-1/user/list/16/3400#3489 all have flags and corresponding tool tips.

My Browser: Google Chrome 80.0.3987.132 (Official build) (64-bits)

Maybe problem with another browser?

<td><nobr><input name="id[]" type="checkbox" value="9621"> <a href="/stats/-1/user/detail/9621"><img src="/image/graph.gif" alt="Detailed stats" title="Detailed stats"></a> <a href="/stats/-1/user/overtake/9621/0/0"><img src="/image/overtake.gif" alt="↕" title="Overtake stats"></a> <a href="/stats/-1/user/list/0/100/Australia#122"><img src="/image/flag/Australia.gif" alt="American Samoa" title="American Samoa"></a> </nobr></td>

I'm also using 64-bits Google Chrome, 80.0.3987.149

Did you try CTRL-F5 on the page (fetch newest version of page from webserver) or clear your browser cache?

Hmmm, I already looked into this and it's quite a mystery to me why this is happening. I'll have another look.