Better discussion hygiene with low-cost comment hint tweak

The problem

Issues conversation thread options, specifically Reply (to this topic) and Write (a new topic) are frequently misused resulting in scrambled issue discussions that are difficult to follow. If we could encourage users to use the product as intended, it would be much easier to follow and contribute to topics.

• Users often Reply to an existing topic thread with an altogether different topic, for no reason.
• Users often submit their reply to an existing topic thread by creating a new topic thread via the Write UI, for no reason.

Final Solution:

For MVC we are simply changing the button text to "Reply" for comments in a reply field vs new comment thread.

Acceptance

• Issue
• MR
• Epic
• Incident
• Anywhere else Discussions are used.

Solution for consideration

To reinforce the desired use of one of our most used features:

• Add a "Create a new topic..." hint to the Write control
• Change Reply hint "Reply" to "Reply to this topic"

@annabeldunstone @andyvolpe