I've been looking into the code that gives the tips bonus, and I've found some interesting stuff, but also it is kind of already expected

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There are probabilities for every bonus given (4) and for every key sequence (8) set for each fight zone (there is usually one fight zone per sector) which the developers could configure.
It is possible to set up a min/max range of time for the tip bonus to appear, as well as a minimum number of romans spawned for the tip bonus to appear.