Hi,
here are some files you should look at to investigate where the space character is coming from:
scala-ide/org.scala-ide.sdt.core/src/org/scalaide/core/internal/repl/EclipseRepl.scala
scala-ide/org.scala-ide.sdt.core/src/org/scalaide/ui/internal/repl/ReplConsoleView.scala
scala-ide/org.scala-ide.sdt.core/src/org/scalaide/ui/internal/repl/InterpreterConsoleView.scala
to set up local environment for building and testing Scala IDE, follow these instructions:
Rafał