I think this is one of the more recent and comprehensive summaries of research on the topic, but in general as I (not a doctor) understand it, the other commenter is right, impacts of any kind are not good for brains, and I think impacts that occur while the brain is already healing from a prior impact are especially not good. Moreover, TBIs can be really minor and have symptoms that are slight enough they’re hard to notice, but that’s when that “impacts that occur while the brain is already healing” thing becomes such a problem - temporary injuries that people don’t realize they have become more permanent.
However, all that being said - with the right therapeutic interventions and given enough time for neuroplasticity to have an effect, physically damaged brains can regain a lot of their function. It’s kind of a scary thing to contemplate when you really start thinking about how fragile the hardware that supports our minds is, but a brain injury is not an insurmountable thing people have to be stuck with the rest of their lives.