Page History

...

Work around is to collapse  the Activity tab when having more then 10 comments to add a new comment.
Please note that settings are saved when you collapse a section, when opening a new Jira issue make sure you have opened the section again.

Pinned Comments (Jira Software)

Keep your team updated on the most important parts of a conversation by pinning comments in issues. This option is only available for Jira Software, not for Jira Service Management!

All important comments you’ve pinned will always appear at the top of the Comments tab, above the other issue comments:

1. Pinned comments: a section that contains all comments that are currently pinned on an issue.
2. All comments: a section with all issue comments, including the pinned ones.

Image Added

• Regardless of the sorting applied, pinned comments always appear in the same order, with the most recent ones displayed at the top. 
• You can pin up to five comments on a single issue, being sure that only essential information is pinned and other users won’t miss a thing.
• Both pinned comments and all other comments are wrapped up in separate sections - Pinned comments and All comments so you know exactly where to look for the needed information.
• Pinned comments appear in both sections. You can edit, unpin, or delete (only added by you) them in either place.

Mentions (tagging)

Mentions (often known as @mentions) are a useful way of drawing someone's attention to a issue or a comment.
When you mention a user, they'll receive a notification by email.

You could also reassign a issue to a colleague for consultation, but that’s a fairly heavyweight operation to just ask a question.
By using @mentions, you can quickly direct conversation in comments to get needed feedback and keep you moving forward.
That way the issue always stays assigned to you and on your radar.

...