I don't know the whole story about Ahtieli and the rest of the playerbase.

But consider this:

1) It's almost impossible to hide your identify while playing somewhat significant character for several years regardless how hard you try. Every player has style, speech patterns, PK patterns, RP patterns, etc.

2) Especially if are somewhat deadly or are outstanding in any other aspect because it attracts others attention and curiousity and they make additional efforts in digging.

3) Especially if you are an ESL person.

Plus, immortals are humans too. They can see IPs and they have snoop, so they can identify a person even against their own wish and more so if they actually wish (and curious). And if a person is alive for several years the leakage happens directly or indirectly, on purpose or accidentally (through hinting posts on this forum, for example, or any other means).