I have replied again on Abhinaba's blog
You said "I have time again seen that people point to intellisense and other editor features to justify or nullify arguments. But a editor feature can never justify design decisions. Not everyone uses VS editor. Moreover a lot of people have build systems that _do not_ use solutions and rely on make files (nmake) or "sources" "dirs" files (NTBuild). Since there is no sln/proj files for the VS editor to use, intellisense do not work and users open CS files individually to edit. This is not a corner case situation and some teams even in MS uses this approach.".
You're right, intellisense can't justify having lengthened/shortend etc Naming conventions, but neither can its use or lack of be used to justify the reverse [I think that makes sense]. I understand that you want to be as verbose as you can in as smaller an area, but I still think verbosity wins the day.
Again for your second class, you shouldn't really be ripping the enums out and using them elsewhere [this could cause unintended consequences, at least having to change the class declaration makes it explicit that you know are changing all the enum refeneces], they should be referenced in the context that they are to be used in, and thus I belive having them in the class where it is initially related is the better choice.
Obviously [and I might condraticy myself now] if you have many classes from the start that use them I agree with your point. But, if you have a file filter [specific to files] and a directory filter [specific to directories] I would keep them at class level named as filter and not at the namespace level named as FileFilter, DirectoryFilter.