This has been happening to me too and it's so flipping ANNOYING!!!!
Here's what I have done, and the problem still persists, but has lessened:
• Turned off read receipts on iPhone
• Turned off individual read receipts under each text thread on iPhone
Now here is a key thing, and I'm not sure anyone has mentioned it (I didn't read the entire thread, so I don't know):
CHECK YOUR MAC'S IMESSAGES
Here's the super annoying part:
• You have to ALSO turn off read receipts under your Mac's iMessage preferences
• Even if you have done all of the above, it will STILL turn on read receipts for individuals - I went through and turned them all off, and I'll sporadically check them, and they'll be TURNED BACK ON for certain individuals, and there appears to be no rhyme or reason to it
This is the ONLY solution I have found - turning it off anywhere I have found for it to be on, but it loves to persist for individual read receipts via my Mac. But at least it isn't doing it as often, although I would prefer for it to not be done at all.
Like seriously Apple, WTF, get your sh** together. I hate Androids and would prefer not to switch over.
Or get rid of read receipts all together.