Historically one of the most heated flame-wars in the Scheme community. We have to decide whether we want to preserve backwards compatibility with standards up through the R5RS, or reaffirm the switch to case-sensitivity in the R6RS. The charter gives precedence to the former, so unless we can reach a rough consensus (> 90%) to the contrary, the default should remain case-insensitive.
Whatever we choose we should realize that some implementations are likely to use a different default in their preferred environments.
Note that the default case-sensitivity is orthogonal to the issue of whether and how behavior can be toggled on a per-file or per-expression basis. If there is a toggle, it may be specified by WG1 for both groups, or only by WG2.
Below are some common arguments for each side.