Hi Amit,
I ran a quick test just now in 6.3.
I get a different error than you, but just to confirm I also cannot release a lock without providing input to the Comments parameter. Here's the error I get:
Internal : The parameterized query '(@eventCode nvarchar(4),@narrative nvarchar(84),@sourceUser uniq' expects the parameter '@comments', which was not supplied.
Respectfully,
Dave
Dave Morris, 3Ci at Southern Company