> there don’t appear to be downsides for overdoing it
There may or may not be a downside depending on what one considers a downside.
In one of my other comments I just made in this thread, I mentioned my experience taking relatively large doses of 20g a day. While I found it has cognitive benefits, it did interfere with my sleep, though not catastrophically. If a person happens to enjoy sleep, then it's probably best they stick to 5 or 10 grams. On the other hand, if you need to pull an all-nighter, the sleep interference (as well as the better recovery the following day) may not be seen as a downside but beneficial.
But yeah, from a toxicological perspective, creatine does seem very safe even at those doses.
Yes, there is always going to be someone somewhere that sees some sort of issue. My point wasn’t that nobody anywhere has ever experienced a negative consequence, but that at scale, it is overwhelmingly safe and so it isn’t really worth advising the general public to tailor their dose.
Any of the rare issues that people do experience—especially at the 5g/day level across age and weight—are minor, acute, and easy to resolve by simply lowering the dose.