Treat comments as more central feature

### Problem Statement

First of all, thank you for building this useful tool! I have some ideas for comments on Sentry issues.

**Features** As noted [here](), the comments could be highlighted better in the UI. It's currently a small box in the activity timeline in the bottom right corner.

Moreover, I noticed that comments cannot be edited, and that formatting (e.g. Markdown) and hyperlinks don't work. In Slack notifications, the comments are not visible at all.

**Big picture**
I believe investing in comments has great potential, as it will allow Sentry to be a central place of communication for teams to manage their issues.

Alternatively, Slack could be this central place of communication for Sentry alerts. This is not without flaws, though. Placing Slack comments on an alert message thread won't propagate them towards Sentry. And when issues reappear, they create a new Slack thread, so it's not easy for someone to trace back any earlier comments made. There are at least two solutions here:

1. All communication could be aggregated centrally inside Sentry; Slack integration just needs to be able read these comments, and possibly add them too.
2. Let alert reappearances not trigger a new Slack thread, but continue the existing thread; this would strengthen Slack as central communication point.

**Example usecase**
Let's say during my tech support shift, there were some alerts that will be fixed by another team's fix ticket. I'd add a comment linking that ticket. If we expect the fix to be definitely ready in 2 weeks, I will snooze the issue for 2 weeks. When the issue still pops up later on Slack, there's a different person handling tech support. Ideally the Slack message already shows my prior comments and knows how to follow up (e.g. check with other team, add a new comment, resnooze).

Curious about your vision and thoughts are on this! Thanks in advance

### Solution Brainstorm

*See above*

### Product Area

Issues

The issue names no files, tests, or entry points; begin by locating the Issues comment UI and Slack notification or integration paths. Before coding, narrow the proposal to one behavior and define its acceptance criteria. Done would require an agreed scope plus tests for that behavior, which the current brainstorm does not provide.

Written by the indexing model from the issue text.