Comment order doesn't change with a activity comment bump. The comment container is just a flexbox column container. So you can reverse its order as you see fit. The following CSS is already included by default based off how many comments there are.
Code:
.cb_template .activityStream .activityContainer:not(.activityCommentsLong) .commentsStream,
.cb_template .activityStream .activityContainer:not(.activityCommentsLong) .commentsStreamItems {
flex-direction: column-reverse !important;
}
If you don't want that you can apply the below using CBs built in CSS overrides feature.
Code:
.cb_template .activityStream .activityContainer:not(.activityCommentsLong) .commentsStream,
.cb_template .activityStream .activityContainer:not(.activityCommentsLong) .commentsStreamItems {
flex-direction: column !important;
}
Basically if there's a lot of comments then the new comment box will be at the top because it's no longer possible to follow it as a discussion thread. Otherwise new comments box will be at the bottom.