Yes, definitely.
It's when they started being super chummy in the DMs, sharing almost everything about the happenings in their lives without regarding the others' time, experiences and even stories.
When they did regard them, they asked for something in return.
When they'd become too comfortable with you, they started showing their true colours. They would not stop shoving their successes onto you, seeking constant praises from you and others, and foul-mouthing everyone they didn't like.
Some I have tolerated and still love their stories. Some I stop following altogether because even the stories' characters emotionally drain other supporting characters and this is no doubt, reflects the authors' interactions with others.
Please take care of your motivation and creative self online, everyone.