Interesting spelling mistakes, I always thought QuickSeller was a native English speaker.
Yes, he is, and that's the point: if you're not an American English native speaker its a bit harder to judge what phrases and misspellings are common versus uncommon.
i bet if you parse through years of my posts, you'll find a few misspellings i've shared in common with probably a bunch of other forum accounts. i really don't find that conclusive at all.
But will you find all of those shared with QS/PN7? Would you even find more than 3 of the 9 examples provided? There's a big difference in odds between guessing 3 correct numbers in a lottery and 4.
There's a pool of users for each individual phrase/word/mistake. The odds of a user residing in a pool with another user go down considerably when filtered by subsequent pools. The pools vary in size from containing liberally 1/8th of all forum users (probably closer to 1/20th, hence they are all "uncommon") to 1/50th, 1/100th or even lower.
Let's just say all pools contain 1/8th of all active forum members for the sake of argument: by the 5th example, you're down to 1 in 32,768 members. And if you cross-reference this with the sections they post in and their total number of posts, it further narrows down the remaining list of members by a considerable degree (perhaps less than a handful).
This Venn diagram example isn't perfect as it would require 3-dimensions and circles of unequal sizes to more accurately portray the overlap of users and words, but it demonstrates the decreasing amount of chance users have with residing in areas of large amounts of overlapping circles.
Quickseller resides in the very center of this diagram. The number of users who fall into all 8 circles (share the same 8 phrase/misspelling similarities) is extremely small. As a matter of fact, I would contend that he only shares it with PrimeNumber7, but I'm welcome to be proven wrong.
Why does it all matter?
I would absolutely find a similar analysis yielding similar results to be valid comparing any two forum members, regardless of their reputation. However, I would only consider it worth publishing on the forum if one of them had a multi-year reputation of being deceitful, dishonest and harmful to other members.
You should only trust PN7 as much as you would trust QS.