The pipe character will get there, all right. If anything, it’s only lower ASCII (below 32) which could be problematic, plus a few reserved characters.
The problem with using a character like a pipe, however, is that much depends on how the programmers are reading/storing/parsing the variables which contain these characters. I haven’t checked to see how these characters arrive in a POST or a GET, or whether any function is required to decode urlencoded strings… but my assumption is that one would be required to urldecode the returned variable as well.
Thus, if IE automatically urlencodes any of the strange characters it finds, but the original link was not urlencoded by the programmer, it is reasonable to assume that the programmer also did not use urldecode to receive the data because he didn’t encode it in the first place.
In a situation like this, it is highly likely that the variable will contain invalid data – which probably results in the default “TYPEIN” being set… and so an affiliate will lose the referral.
Of course, a URL which does not have characters requiring urlencoding will not have this problem – so why construct the link with these characters in the first place?
Referback may not intentionally have done this, of course – but they need to resolve this issue by removing the strange characters to ensure compatibility across all browser platforms and versions. For the record, IE6 displays the links correctly without modification. IE7 automatically urlencodes the link.
BTW, Partnerlogic uses a single pipe in their URLs – and IE7 does *not* urlencode the single pipe.