[gambiting]

Bear in mind that in some languages this problem doesn't exist. In Polish for example, all female names end with an "a". There is not a single exception from that rule, so if you see a name ending with an "a" it is always a female name.

[TillE]

And in Iceland you can reliably determine gender from a person's second name, ending in either -son or -dottir.

[zuppy]

Yes, but probably there are people in Iceland and Poland with foreign names. I know that you both wanted to explain that there is a rule in some language and it's nice to find out about that information, but as long as it doesn't apply to everybody, I don't consider this a solution.

[gambiting]

In Poland you cannot give children foreign sounding names. So unless we are talking about foreigners visiting,then it does apply to everyone. Like I don't know a single person to whom that rule would not apply.