The word doesn't seem to be used by itself however - the code in the article contains "user_klass" and "log_klass", which can presumably be spelled correctly without causing an issue?
Yeah, it can, but perhaps you develop a habit for it whenever creating variable names, so there is some visual harmony between klass, old_klass, klass_dismissed, etc. when reading the code.
The k is a useful visual hint, even when not necessary.
I think perlgeek was referring to the use of user_klass and log_klass.