First thing is to check that Postfix (or whatever is adding the name) is properly encoding it. On the messages in question received on your laptop, view the message source and look at the From: line. It should start with something like
=?ISO-8859-1? or
=?UTF-8? - only 7-bit ASCII is permitted in mail headers, and
RFC 2047 defines how to encode 8-bit characters. (For example,
=?ISO-8859-1?Q?Andr=E9?= encodes the name
André.)
If this is happening, then the most likely issue is a character set mismatch. Look at the character set being used to encode the header (it's immediately after the
=?, or ISO-8859-1 in my example) and compare it to the locale being used in your terminal where you set your user's full name. In the case of a mismatch, then Postfix is probably using a different locale than the one where you set the name.