I would assume that if "probability that other users will positively engage with a tweet" is the primary determiner of reach, then the more you can help Twitter accurately predict that probability, the better, because otherwise the default probability is likely no higher than middle-of-the-pack.

If that assumption holds, then I would guess this type of algorithm favors consistency of content. In other words, someone who picks a certain topic and consistently tweets only about that topic is going to be easier to form predictions around versus someone whose tweets show much more variety, in topics, styles, etc.

What that might mean, from a "gaming the system" point of view, is that if you're a person who intends to primarily tweet about two or three disparate things, you might be better off creating a separate account for each, rather than a single account where engagement is harder to predict.