Inconsistent Markdown headers rendering issue

[Fred-Vatin]

🏷️ Discussion Type

Bug

💬 Feature/Topic Area

Code Search and Navigation

Body

Description

For about a month, headers using the ## Markdown syntax have been rendering inconsistently. Within the same document (issues, discussions, etc.), some headings render correctly as HTML H tags while others remain as unrendered plain text (e.g., displaying literally as ## Section).

This layout issue is present in the preview tab and persists in the published message for all readers regardless of OS or browser.

Reproduction Steps

1. Create or edit an issue, PR, or discussion on GitHub.com., even a READ ME
2. Enter Markdown text containing multiple headers, for example:

## Section 1

### some H3

Some text

## Section 2

### other H3

Some other text

3. Click the Preview tab.
4. Observe that one or more titles randomly render as plain text instead of formatted headings.

Workaround

To fix the rendering issue temporarily:

1. Remove the ## prefix from the affected line.
2. Switch to the Preview tab.
3. Switch back to the Write tab, re-add the ## prefix, and check the preview again.

Additional Information

This bug occurs intermittently, bug its frequency has increased significantly in recent weeks.
Because it is a recent but that affect every OS and browsers, I opened a ticket but it has been auto closed a virtual assistant.

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