The 25-year-old was spotted by TV cameras applauding Raya's fine save during the first half of Sunday's 2-2 draw with his hands above his head while sat on the substitutes’ bench.
Ramsdale appears to have lost his starting place to loanee Raya, who has now started three games in a row including the club's first Champions League game in seven years and now the north London derby.
Speaking on Sky Sports after the game, Liverpool legend Jamie Carragher believes Ramsdale's celebrations were insincere. He said: "I thought it was like the Oscars, you know when someone loses the Oscar and they start clapping and smiling for the other person.
"I was laughing when I saw that. He's absolutely devastated with that really."
The remarks reportedly promoted a furious reaction from Ramsdale's father, who posted on X (formerly Twitter): "You are a Disgrace!! Show some class!! My lad has."
And now Ramsdale has taken to Instagram to post two photos of him celebrating standout moments by team-mates.
The first is of Ramsdale, who is a substitute, celebrating Bournemouth beating Forest Green Rovers in the Carabao Cup second round four years ago, following heroics from fellow goalkeeper Mark Travers. The other is of him celebrating Reiss Nelson's 97th-minute winner against Bournemouth last season.