It will work

Not the way it was posted. At least, StringBuffer.setCharAt() needs a second argument of type char, and this would be a strange type for a "customer name" field.

Rule "Wild char validation"
When
c: CustomerInfo(name : customerName matches ".*([\*#].*") //any string containing a * or a #

There's a syntax error here, use ".*[*#].*", because you don't need to quote '*' inside '[...]', and if you do (which is OK) you'll have to use '\\'.

then
modify(c) {
setCustomerName(name.replaceAll("[\*#]", "")); //replace any * or # with ""
}
end

Same here: either no '\' or doubled.

-W