I too get the same "this, that".
It might depend on the what is used as "comma".
On my system, one thousand is written "1.000,00".
So: "%_WINVER" is "5,2"; "%@eval[%_WINVER - 6]" is "-0,8".
And it is possible that the comma between 0 and 8 is considered as an argument separator.
If I write "echo %@if[%@eval[0,8] ge 6, this, that]" I get " this, that".
If I write "echo %@if[%@eval[0.8] ge 6, this, that]" I get " this".
Regards
Rodolfo Giovanninetti