I had a quick look at clm's params file and did not see evidence of this parameter. However, the line that you quoted above suggests that you can change the value of this parameter using user_nl_clm. And there may be a default value that gets used when the parameter is not explicitly set.
So first I suggest this:
If you have been changing the value directly in the code, then try changing the value using your case's user_nl_clm.
If answers still do not change, I suggest tracking down the parameter throughout the code and adding write(iulog,*) statements to confirm the parameter's value everywhere that it appears. You could also add write statements for other variables where the parameter gets used, in order to develop an understanding of why your changes seem ignored.