Hide Alerts turns on 'by itself' for certain contacts in Messages

Hide Alerts turns on 'by itself' for certain contacts in the messaging app. I just checked and 12 of my message threads (out of about 500) showed the Hide Alerts flag (crossed-out grey bell) without me having ever consciously enabled it. There was no clear pattern, except alerts were hidden for all the contacts I most frequently txt with, plus a few less frequent contacts.

Numerous people have reported this issue since about Feb 2021, on this forum and on many other Internet forums. I think it's time that Apple Support accepted that it needs to investigate this problem more deeply.

From my limited evidence, and that of others, it does seem that it is more likely to happen the more often a particular contact is selected. However, if the UI is causing issues, Apple's philosophy has always been to take responsibility for improving the UI, not to blame the user for using the UI wrongly.

In the past Apple Support has recommend restarting the iPhone and updating to the latest iOS, with apparently no evidence that either will help. Then one response said:

it's likely something to do with the way you operate the device, and then inadvertently enable this.

I know of only two ways to Hide Alerts for a specific individual, both of which are nigh-impossible to activate inadvertently. This Community Specialist should not have made this comment unless they had actually identified a way to activate it inadvertently:

1. Tapping on an individual's icon at the top of their message thread, then moving the Hide Alerts slider that appears lower down the screen. This slider does not even enable by just tapping it, it has to be slid precisely and explicitly.
2. From the screen that lists all message threads, one contact's thread can be swiped to the left to reveal two icons: hide alerts and delete thread. I attempted various "slidey taps" and "tappy slides" to see if I could select the Hide Alerts icon inadvertently, but the thread has to be slid fully to the left, then released, then the hide icon tapped separately, which is again nigh-impossible to do inadvertently.

[Re-Titled by Moderator]