文本文件处理需求：移除高亮标记并将标记内短语空格替换为下划线

Hey there! Let's walk through exactly how to format your content using Markdown, following the guidelines you shared—here's a clear, practical breakdown:

• Headings: Use number signs (#) at the start of your line. The number of #s maps to the heading level: one for a top-level main heading (# My Main Title), two for a subheading (## Key Section), and so on up to six levels total.
• List items: Kick off each unordered list item with a dash (-). No extra fluff needed—just a dash followed by your content, and you’re good to go (nesting works too by indenting sub-items under the parent).
• Emphasize text: Wrap the text you want to highlight with asterisks (*). Use single asterisks for italicized text (*this is italicized*) or double asterisks for bold text (**this stands out more**) depending on how much emphasis you need.
• Code or commands: Surround inline code snippets with single backticks (`), like `git commit -m "Update file"`. For longer code blocks, use three backticks at the start and end of the block (you can even add a language tag right after the opening backticks for syntax highlighting, e.g., ```python).
• Quoted text: Prepend each line of quoted content with a greater-than sign (>). This is perfect for citing others or pulling in external context, like:

  This is an example of quoted text that will visually stand apart from your main content.

• Links: Structure links with square brackets for the clickable display text, followed immediately by the target URL in parentheses. For example: [Stack Overflow](https://stackoverflow.com) will render as a clickable link pointing to the site.
• Images: Similar to links, but start with an exclamation mark (!). The square brackets hold descriptive alt text (critical for accessibility), and the parentheses contain the image’s URL. Example: ![A Screenshot of the Dashboard](https://example.com/dash-screenshot.png)

内容的提问来源于stack exchange，提问作者Yunan Zhang