If you are wearing a messenger bag, why the heck are you wearing a dress shirt or suit anyway? On casual jackets, no big deal - the more worn in the jacket, the better it usually looks in most cases. And the strap does nothing to tee shirts and twill shirts that multiple washings won't do worse to anyway. My solution is to never wear suits except to interviews (in which case I use a briefcase or carry a leather portfolio) or to weddings and funerals, both events to which bringing supplementary reading material are considered bad form. Wierd academic tradition: the lower the position you are seeking, the better dressed you need be for the interview, excluding administrative posts. If you are interviewing to become the chair of a department, for example, you could wear Eccos, chinos, and a "dress shirt". Maybe a jacket, if you are feeling especially formal. If you are applying for an assistant professorship, most likely you're going to be dressed like a I-banker.