I started digging: the problem doesn't seem to be xowiki specific, but rather in the lc_parse_number procedure.
In a system with it_IT locale installed, executing
lc_parse_number 12,00 it_IT 0
which should return the number 12 in whatever form, the result is 1200 instead.
lc_parse_number 12,00 it_IT 1
parses the number correctly, as we are forcing the proc to treat the number as integer, but I think it should be able to understand the real nature of the number in both situations.
I will look further
