While working in the gradebook, some users reported that it was not accepting "aggregationcoef" with commas, altough they are showed this way on the interface. Debugging the problem, i found that it is on the PARAM_NUMBER, that only does a type cast on $param.
To work with localized numbers, it must first perform a replace of 'descsep' with '.' and then do the cast.
There is a patch attached to correct this issue.