You should use a real source code editor like Notepad++, never use Notepad. Then you can change the encoding to "UTF-8 without BOM" (this is the only encoding that you'll ever need with AMX Mod X).
It's certainly possible that you discovered a bug in 1.9. You could try 1.10 to see if it's till an issue there so that you can be sure that it's still an issue in the current development version of AMX Mod X.
EDIT:
Looking at
the code, it looks like the functionality is meant to be in there but it looks like they refactored how they read the file since 1.8.2 so it's not unlikely that something broke.
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