Currently this is by design. We are considering having rename search the comments, but what happens when the parameter name you are renaming is a common word? VA cannot assume that all instances of this word, in all comments in all files should be renamed.
That is true. I'll have a look tonight what Netbeans does in this situation, though I suspect that it will splurge all over the comments with the rename.
How often do you use a common word for a variable and not a compound made of several?
On the side of changing comments, the renaming of comments will allow 3rd party references to change too (as in @CMyClass in Doxygen)
Parameter names, if you are avoiding "Hungarian" format (a discussion I do not intend to get into ) then "common" names can turn up quite often. Bool parameters like "print" or "create" immediately come to mind.
A related situation is three functions in a row, all taking a parameter with the same name. This is fine, so long as you know which comments go with which functions, but there are cases where this is not clear.