Those who wish to hodl should br encouraged,
Those who wants to spend it for a currency should do so,
Those who wants to trade it on the market can have their go at it for sure.
It’s just bitcoin being used as it should be.
Yes.. they can do what they like, but some of those things might not be very smart, especially if you might want to get to fuck you status.... but hey whatever, each person can do what they like, and you have made your point... but it does not mean that they even know what the fuck they are doing, and if we are focusing in this thread upon what we might believe is a "good bitcoin investor" then selling all of your BTC does not seem to make a good bitcoin investor, but hey do what you like.. if you want to sell all of your bitcoin, then hopefully you do not end up selling too many too soon and then becoming bitter... especially since bitcoin is actually a vehicle to one of the greatest (if not the greatest) peaceful wealth transfers, in history, and if you want to fuck around with trading and trying to buy back cheaper, that is upon you to take those kinds of chances.. You are free to do so, and king daddy gives no shits if you end up having to buy back 50% higher because you ended up having the wrong mindset and you ended up selling too many too soon because you thought that you were smarter than everyone else.. like a smart virus.

Everyone can do whatever they like, which is a good point. But I agree with what you said that it will be something you regret later. I think, a good point is not necessarily going to bring something big that we really want, and it is our job to make that good point even better in the future, and bitcoin has all the criteria.
We will be able to feel something very big when we sell bitcoin, and I am sure for people who bought when the price touched 15k some time ago, they will get a big profit when they sell today at 29k as I write this. But is that what we really want? Of course not. The current price is still far from the last ATH price, and I personally have faith that bitcoin will be able to reach a new ATH, yes although I can't be sure when exactly that will happen. But my belief is based and for me it is a very good thing to continue to hold it.
There are likely some BTC investors who sold BTC around $20k or below $20k because they ended up panicking, and even coming up with a theory that BTC prices might go down to $12k or even lower, but we know that $12k or lower did not happen because the lowest that we got was about $15,479.
Furthermore some of those folks who sold BTC around or below $20k may well have bought their BTC on average for much lower prices, so in terms of dollars they may well have gotten a profit, so technically they might not be incorrect in terms of experiencing dollar profits.. but they also might end up having to buy back at way higher prices in the future because they ended up having way too few BTC and perhaps no BTC because they did not employ sufficiently prudent and/or smart BTC investment strategies, even though at the time that they sold their BTC they were thinking that they did the right thing, especially given the then circumstances and their view of what they thought bitcoin would do (even though they ended up being wrong).
Historically, we have a lot of similar circumstances in which guys are bragging how smart they were on some of their BTC trades, and surely they may have even made decently large dollar profits, but then they end up hardly having any BTC when the BTC price goes up they are not prepared for UP.. even if they already made a lot of dollar profits, and sometimes the BTC price goes up several times or even 10x, and does not end up coming back down, and even if they were to later invest into bitcoin, they might ONLY be able to purchase a fraction of their previous BTC holdings, maybe even in the category of 1/10th the amount... so sometimes it can take a while to figure out if someone is a smart/good investor or not, even if they might make some moves/trades that seem to be smart and profitable.
Yes, it's not possible anymore, but I'm sure that many of them do this kind of thing, there are several reasons, one of which is because they panic, and what we see a lot of is from those who are already from the beginning to take advantage in a short time, and they keep doing it. They still get benefits, but in this case there are things they might miss, namely when suddenly bitcoin moves up they will be a little behind.
I prefer those who sell bitcoin because their original intention was only to take advantage of a short rise, rather than those who panic because some people say that bitcoin might touch a price lower than the lowest price bitcoin reached some time ago. I have seen some of them saying that bitcoin will hit 12k or lower, like you said, so they decided to sell their bitcoin because they want to get the lowest price. Not wrong, but if we prepare from the beginning for that possibility, we don't have to sell bitcoin quickly, because of course with careful preparation we will be prepared to buy back bitcoin at the lowest price. Most people like that are not committed to what they planned at the beginning.