I downloaded that deck and the styling on the cards is arial font. If you changed it, make sure you did it according to the steps here. (Actually you can also just replace arial with your preferred font, in quotes if there are any spaces, but then if you sync to mobile devices, you may not see it there)
Can you share a download link for the font or just its name? (I don’t see it’s used in the shared deck)
If you can’t post links because you’re new to the forum, you can work around that by using the forum editor’s Preformatted text option.
The issue happens in all major browsers I tested (Chrome, Firefox, and Edge). Curiously, text editors like notepad and BabelPad don’t have the issue.
Not sure whether this can be fixed but will post an update if I find something.
A workaround for now is to remove this diacritic as it’s probably not essential to understanding the text. Copy the character from the linked page and use Anki’s Find and Replace feature to remove it from all cards in the deck.
@abdo I also am using Windows 11, and here is what the same card looks like on my system, with no changes made to the styling, at least in preview. I don’t know if this is right or not, but it is somehow different.