list traffic in iso-8859-6?

is there any particular reason why a couple of the messages that have 
been posted here recently (one by Dave, one by Bruce) have used charset 
iso-8859-6 (Arabic)?
reason I ask is, my Mac Mail client displays the digits in Arabic (e.g. 
"rfc٢٨٢١" rather than "rfc2821").  I'm not sure whether that's 
consistent with iso-8859-6 or not, but it does make the messages 
difficult for me to read.
Keith