I ask for your opinion on the subject, especially those of you who have more experience in catching alts and with address analysis, before taking an aggressive approach or opting for a neutral tag.
Account obviously changed hands, no questions about it as English level deteriorated noticeably and that's something that doesn't happen (unless owner suffered from stroke or some similar far fetched scenario).
There are threads you can report plagerism to.
I am pretty sure thta Op knows about that, but he is more curious about whether account changed hands. Question that remains though is how come no one reported him for plagirism yet?