Instead of writing about purity and impurity all day he could have spent that time improving the IRC server to the point where the authentication can not be trivially replayed in what is a clear text protocol and implemented IRC over SSL/TLS.
That sounds a bit snarky; it just seems like purity/impurity is the favorite bikeshed for haskell programmers.
> I will also add OpenSSL support using the HsOpenSSL package which seemingly makes the whole process trivial.
Sometimes people like to write about their pleasant experience before the project is completely finished. I'm bookmarking the project as a good example of Cabal Project structuring and use of some network libraries. Good examples like these aren't very well curated from the universal Haskell repertoire.
He only used part of the blog post to talk about purity; when explaining how the code is designed and organized, it's not like he could reasonably skip that part. Besides, Haskell makes the distinction sufficiently natural that it does but take much effort when actually coding, so the main "cost" in terms of time was probably in writing the blog post :P.
Since it's an internal effort, simplicity trumps security and features. I doubt making the IRC server more complete would be worth the effort and maintenance cost. It's much better to add features only of they are obviously missing when they actually use the server.
That sounds a bit snarky; it just seems like purity/impurity is the favorite bikeshed for haskell programmers.