I noticed some issues when you filter the replies at a topic.
All screenshots were taken at the Trust Level Permissions Table (inc Moderator Roles) topic.
When the user whose replies you filter is the topic author the filter shows one more topic than the filter indicator
When you click one or more “show hidden replies” the number of replies in the progres bar is not changed.
If you click the first “show all replies” the user shown at the banner at the bottom is changed to the user who wrote the first reply.