As of SERVER-5092 the server logs its initial startup banner with LogComponent::kDefault, which renders as "-". Example:
2014-10-10T15:47:59.291-0400 I - [initandlisten] MongoDB starting : pid=34519 port=27999 dbpath=/data/db/sconsTests/ 64-bit host=MacBook.local 2014-10-10T15:47:59.291-0400 I - [initandlisten] _DEBUG build (which is slower) 2014-10-10T15:47:59.291-0400 I - [initandlisten] 2014-10-10T15:47:59.292-0400 I - [initandlisten] ** NOTE: This is a development version (2.7.8-pre-) of MongoDB. 2014-10-10T15:47:59.292-0400 I - [initandlisten] ** Not recommended for production. 2014-10-10T15:47:59.292-0400 I - [initandlisten] 2014-10-10T15:47:59.292-0400 I - [initandlisten] db version v2.7.8-pre-
Add a log component specifically for the server's single-threaded mode and change these messages to eliminate the "-".