I'm not sure what you're doing or how you're getting that. Maybe you have an empty column at the end which simulates a trailing comma.

Using this code, I didn't got the comma.

BCP.exe "Test.dbo.Table" Out "C:\Table.csv" -c -t"," -SMyTestServer -T -m10 -e"C:\Table.err" -o"C:\Table.out"

I noticed that you posted slashes instead of dashes and you had the data_file in an incorrect position. I'm using a trusted connection because I have Windows Authentication, but you're including user and password for SQL Server Authentication so that's the only difference which shouldn't affect the file format.