Fix various problems (#37077)

Quick fix for 1.26.

* Slightly refactor NewComment to fix incorrect responses, remove
incorrect defer (still far from ideal)
* Avoid `const` causes js error in global scope
* Don't process markup contents on user's home activity feed, to avoid
js error due to broken math/mermaid code

* Fix #36582

---------

Signed-off-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>

options/locale/locale_en-US.json

@@ -1531,6 +1531,7 @@
   "repo.issues.context.edit": "Edit",
   "repo.issues.context.delete": "Delete",
   "repo.issues.no_content": "No description provided.",
+  "repo.issues.comment_no_content": "No comment provided.",
   "repo.issues.close": "Close Issue",
   "repo.issues.comment_pull_merged_at": "merged commit %[1]s into %[2]s %[3]s",
   "repo.issues.comment_manually_pull_merged_at": "manually merged commit %[1]s into %[2]s %[3]s",