Increase Character Limit to 4000 in Comments

#### Description
Currently, the character limit in comments and replies (in the 'Comments' tab) is limited to 1000 characters. However, users have reported this is too little, and we need to increase the limit to 4000.

#### Dependencies
Are there any dependencies?

#### DOD
- [ ] Increase character limit in comments to 4000
- [ ] Increase character limit in replies to 4000

Start by locating the validation for comment and reply lengths in the repository, then trace both the Comments tab and reply submission paths. Confirm where the current 1000-character limit is enforced and verify that both comments and replies accept up to 4000 characters when the change is complete.

Written by the indexing model from the issue text.