BuddyPress Message Reply Restrictions section allows you to configure message reply based restrictions for your site members.

Here is a screenshot showing Message Reply Restrictions.

1. Restrict message replying?:- You can use it to enable or disable restrictions on sending new message reply. All other messages replying restriction options are only applicable if it is enabled.

2. Who can reply?:- This option will allow you to restrict new message reply by user roles.

3. Message shown to replier:-  This is the notice which will be shown to the replier if they can not make new replies.

4. Apply threshold limit?:- This option allows you to set a maximum limit of replies which an user can make. You can disable it to set no limit for the allowed roles.

5. How many reply a user can make:- If threshold is enabled, this is the maximum number of allowed replies.

6. Apply duration?:- You can either set a limit for the lifetime or use this option to apply the limit for a certain duration. It allows you to setup a rate limiter like 20 replies per day.

7. During the time(in minutes):- If apply duration and threshold is enabled, it allows you to setup the duration after which the limit will be reset.

8.Notice to shown when the threshold limit reached:- Set a default message to showing a user after threshold time out.