In various jobs over the last twenty years, I've been involved in hiring programmers several times. We advertised for a graduate role at one point. We received six hundred CVs for one job. Obviously, at that point you have to find some sort of winnowing method. We chose "proofread the covering letter" as our approach. Basic errors got rid of about 250 CVs that way. We did specify that writing skills and the ability communicate with clients were a priority for us. Ho hum.
I'm not sure about the casual dress issue. It does indicate to some extent how much importance the applicant places on the interview. On the other hand, I'm generally looking to employ someone based on their programming skills and their ability to interact with coworkers so it's not exactly an issue for me.
I met a chemical engineer the other day who told me that communications and writing skills are now part of many chemical engineering degrees. Is that the case with CS these days?