Citing technology media MacWorld, some iOS/iPadOS users reported that their contacts could still see when their messages were read even though the Send Read Receipts feature in the Messages app was turned off. Apple has built a system-wide setting across all of its platforms that you can use to turn the feature on or off.
Regarding the description of the feature, Apple officially wrote: You can send read receipts so that the message contacts know you have read their messages. You can send read receipts for all conversations or just a conversation. If turned on for all conversations read receipts, you can still turn off read receipts for individual conversations, and vice versa.
Macworld’s Glenn Fleishman explained that the issue had briefly cropped up in previous iOS versions, but in iOS 15 it appears that more users than ever are experiencing a disconnect between their settings and reality. It’s unclear how widespread the problem is, or if Apple is aware of it.
If you happen to notice that your contacts can see when you read their messages despite your read receipt setting, you can try restarting your device. Some iPhone and iPad users have been able to temporarily fix the problem this way, but it’s not a permanent solution, according to Macworld.