1. I'm not sure I understand the complaint about arguments. From you example it looks to me like the problem is that Scala requires type declarations and supports default arguments. I don't understand how this is worse than the equivalent Java example. I also don't understand how the Ruby version is inherently better. The only difference seems to be static vs. dynamic typing.
2. I don't understand how Play 2 screwed over Scala developers. It seems like Play 2 is much better for Scala developers. Scala is now a first class supported language instead of just an add on module. I also don't understand how Play 1 was 'the' thing that was bringing web developers to Scala. It wasn't in any way a core part of the framework. It was just something you could optionally use. Scala is something you could optionally use in any Java web framework.
2. I don't understand how Play 2 screwed over Scala developers. It seems like Play 2 is much better for Scala developers. Scala is now a first class supported language instead of just an add on module. I also don't understand how Play 1 was 'the' thing that was bringing web developers to Scala. It wasn't in any way a core part of the framework. It was just something you could optionally use. Scala is something you could optionally use in any Java web framework.