Did you ever figure this out? I had a slightly different problem... and slightly different requirements, so I'm not using the batch processing... I had to create my own "batching" because I needed more flexibility.
ANYWHO, this is where my problem was:
ILogRecordset queryResult = logQuery.Execute(sbQuery.ToString(), inputFormat);
var sbOutput = new StringBuilder();
for (; !queryResult.atEnd(); queryResult.moveNext())
sbOutput.AppendLine(queryResult.getRecord().toNativeString(", "));
queryResult.close();
When I removed that comma, the delimiter was a space, as expected.
I hope this helps...