Following the recent Bitcoin ATHs, C0inbase subredditors are now gaslighting people that storing your coins on that exchange is more secure than self-custodying.
You said Coinbase subredditors
Coinbase is an exchange and there are some people there on the Coinbase subreddit that may just like to mislead people.
I am not active on Reddit but the best forum I know that I can see the true information about what bitcoin and exchanges is still on this forum, Bitcointalk.
You saw what Binance CZ posted about this when people were moving coins from Binance to a noncustodial wallet in 2022. Those that are working for an exchange may just like to mislead people and they may be the one posting it.
Bitcointalk is the most unbiased and trustworthy platform. Reddit, especially moderated subreddits dedicated to a certain company, is full of shit. I'd never take an advice from Redditor because I've seen many biased posts here and unlike Bitcointalk, there is no legit trust rating on Reddit. Coinbase also has in its terms that it can confiscate your money at any time without further explanation. Exchanges are not only unsafe for storing your cryptocurrencies, these days it's even dangerous to trade on them because you should expect problems from them at any time when you decide to withdraw.