i don't think apostrophes are counted as a difference in a name. for example, i had a king named fool's gold. upon just looking it up in search, "fool's gold" gives no results, but looking up "fools gold" does, and that king's name does use the apostrophe.
so you can use apostrophes, but i dont think it counts as a unique symbol. if someone has that name, you won't be able to use it.

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Now that I think about it, when kings are inactive for a certain period, their king aren't listed to avoid cluster. Could possibly be the reason that the searches didn't pop up?

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"if you decide to take a hiatus from Lioden and you're attached to your leader's name, you may wish to rollover at least once per year. Your leader's name will be reset if you are inactive and do not rollover for an entire year. This is because leader names are unique, so only one leader can have a certain name at one time. If you return to the site and someone else took your leader's name while you were gone, you'll have to wait for them to change their leader's name in order to get it back."

(Source is Lioden Wiki)

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