When a function object is given to describe function documentation is not shown (it's shown on the symbol). Because of this, the slime function documentation doesn't show it either.
Index: src/org/armedbear/lisp/describe.lisp
===================================================================
--- src/org/armedbear/lisp/describe.lisp (revision 14850)
+++ src/org/armedbear/lisp/describe.lisp (working copy)
@@ -89,7 +89,13 @@
(setf plist (cddr plist))))))
(FUNCTION
(%describe-object object stream)
- (describe-arglist object stream))
+ (describe-arglist object stream)
+ (let ((function-symbol (nth-value 2 (function-lambda-expression object))))
+ (when function-symbol
+ (let ((doc (documentation function-symbol 'function)))
+ (when doc
+ (format stream "Function documentation:~% ~A~%" doc)))
+ )))
(INTEGER
(%describe-object object stream)
(format stream "~D.~%~