> Another traditional issue with Japanese codecs is that people have different opinions on what the encoding should do. It may be that when we release the codec, somebody comes up and says that the codec is incorrect, and it should do something different for some code points, citing some other applications which he considers right. In particular for the Microsoft ones, people may claim that some version of Windows did things differently.

In regard to e-mail encoding, Japanese should use utf-8, then it
resolves most problems. However, for historical reason or
compatibility reason, it's different even today. I don't think these
legacy codecs are needed for individual application, but we sometimes
encounter an encoding issue when an application collaborates to
external system like e-mail.

> Now, for this set, the ones that got registered with IANA sound ok (in the sense that it is our bug if they fail to conform to the IANA spec, and IANA's fault if they fail to do what users expect). For the other ones, I wonder whether there is some official source that can be consulted for correctness.

Exactly. Now, I'm finding euc-jp-ms and iso-2022-jp-ms spec in
English. Of course, there's a voluntary document in Japanese as
follows.
http://www.wdic.org/w/WDIC/eucJP-ms
http://www.wdic.org/w/WDIC/ISO-2022-JP-MS

I may agree with dropping character encoding which is difficult to
find official source.

> On a different note: why do you claim that the code is written by Perky? (it's not you, is it?)

Right! Because the credit belongs to him. I'm an assistant.