It makes you a target to hackers and scammers. Anyone can see your complaint and attempt a social engineering attack if your account is public, so it would be better to e-mail or call them using the office information provided via their website.
The messages are not encrypted, meaning Twitter, Facebook and Instagram can see your messages if they wanted to they could impersonate you.
Earlier this month Twitter was hacked impacting accounts belonging to Barack Obama, Joe Biden, Bill Gates, Elon Musk, Kanye West, Kim Kardashian West and Warren Buffett.
The attacker infiltrated the high profile accounts targeting their followers using the common Bitcoin giveaway scam, “Send 1 Bitcoin to the displayed address and receive 1.5 Bitcoin back.” It's a social engineering method, attempting to gain money off of unsuspecting victims. https://decrypt.co/35784/5-key-things-we-learned-from-the-twitter-hack
https://www.cnn.com/2020/07/16/tech/twitter-hack-security-analysis/index.html
https://www.bbc.com/news/technology-53439585