sure, not denying that. my writing style is fairly different now in my 40s than it was in my late teens/early twenties.

but, those changes are usually pretty gradual and relatively small. thats why when attempting to identify someone via writing, you look at several aspects of the writing and not just word choice (grammar, use of specific slang, sentence length, paragraph structure, punctuation, etc.). it is highly unlikely that all aspects of someones writing changes at the same time. simply removing "ha" is inconsequential to identification if not much else changed.

additionally, this data is typically combined with other data/patterns (posting times, username (themes, length, etc.), writing that displays certain types of expertise, and more) to increase the confidence level of correct identification.