According to
Bitcointalk's seclog, passwords have not been changed for the account "altcoinUK" (at time of posting since Dec 19, at least).
However, last post before today had been posted on August 28, 2016, 05:44:36 PM. If it was sold or transferred to a third party (which indeed at first glance on the writing style transformation appears to be the case imo) it seems that this happened at some point after that date, and perhaps the new "owner" deliberately waited to post until today.
On another note, it could very well be the same man or woman, given that "altcoinUK" has been a controversial figure before. Some people may very well change their writing styles (and even intentions) -- even on purpose.