I think it has to do with karma count.

I had two accounts, one had been scrubbed and was mostly used for commenting, and the other was a porn alt.

The porn alt has hundreds of thousands of karma and it got multiple IPO messages while the original, older account got nothing due to being sub 5k on posts.

Edit: Suspicions confirmed!

Reddit is planning six tiers of early access based on each “participant’s contributions to Reddit,” the company said in its updated SEC filing. Those tiers are based on a user’s “karma” score, ostensibly an aggregate total of up/down votes on posts and comments.

The first tier of users will be those “who have meaningfully contributed to Reddit community programs,” though what that means isn’t explained more clearly. After that come tier 2 users, who must hold at least 200,000 karma points or have taken at least 5,000 moderator actions. Tier three includes users and moderators who hold at least 100,000 karma points and have taken 2,500 moderator actions. Tiers 4 and 5 are each half of the previous tier’s total, and tier 6 includes everyone else, with a waitlist available if the total number of shares purchased exceeds the original 1.76 million.