Section 6.2.9 of the core spec explains the usage of the //eb:Error/eb:ErrorDetail element as: "provides additional details about the context in which the error occurred. For example, it may be an exception trace".

The ebMS XSD defines the type of this as xsd:token. According to the XML Schema specification this means the value of this element must "not contain the carriage return (#xD), line feed (#xA) nor tab (#x9) characters, have no leading or trailing spaces (#x20) and have no internal sequences of two or more spaces" (quoted text taken from XML Schema spec).

I think the type definition unnecessarily limits the text that can provided and makes it more difficult to provide a useful context of the error.