Hello,
just an idea
There are lots of wrong reply (when the target post is the latest in the topic. Especially on mobile.) on our forum because they use the blue reply button on the bottom of the topic. Those replies are not user specific… so might be the real recipient is not notify. Except if they mention someone.
It might work some little notification when they click the Reply button to choose which post they want to reply. The OP or the latest in the topic?
Something like this: Are you sure you reply to the OP? (highlighting with the OP and the latest post) and this message is gone after ~5 sec automatically by confirming the reply to OP if they didn’t choose. It’s only appear when they use the blue Reply button on the bottom and if there are replies on the topic. Just to make sure they want reply to the OP or the latest post.
It maybe can works like when try to reply an other topic the system asks which topic you want to reply with a little notification than you can choose.