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