add comment on the motivation as suggested by aviatesk

Author: nsajko

src/julia/kinds.jl

@@ -105,6 +105,8 @@ function _register_kinds!(kind_modules, int_to_kindstr, kind_str_to_int, mod, mo
     _register_kinds_names!(int_to_kindstr, kind_str_to_int, module_id, names)
 end
 
+# This function is separated from `_register_kinds!` to prevent sharing of the variable `i`
+# here and in the closure in `_register_kinds!`, which causes boxing and bad inference.
 function _register_kinds_names!(int_to_kindstr, kind_str_to_int, module_id, names)
     # Process names to conflate category BEGIN/END markers with the first/last
     # in the category.