Proposal: use color for markdown headings instead of centering

[llimllib]

Why?

• Centered headings are too far from the text they're introducing, which is distracting
• Similar software uses colors; it's what users expect. cf [QUESTION] How to override markdown header justification? #2137 and How to make markdown headings be left justified? #2413 for example, and the screenshot below
• Rich is already using colors for markdown rendering, so there doesn't seem to be a reason to avoid them
• It simplifies the Heading code - the patch is -11 lines of code
• personally: I would like to use rich in my terminal for rending LLM output, but the centered headings are too difficult to read

Visual Comparison

Below is a series of renderings of a simple markdown document:

• A simple proposal I made (diff below)
• glow
• bat
• rich as it currently stands

The diff

I do not have strong feelings about the colors involved, and I just copied glow's colors because I thought they looked alright. I would be happy with any particular colors, as long as the headers were left-justified and used color to distinguish themselves

diff --git c/rich/default_styles.py w/rich/default_styles.py
index 3a0ad83a..b7df322e 100644
--- c/rich/default_styles.py
+++ w/rich/default_styles.py
@@ -153,13 +153,13 @@ DEFAULT_STYLES: Dict[str, Style] = {
     "markdown.item.number": Style(color="yellow", bold=True),
     "markdown.hr": Style(color="yellow"),
     "markdown.h1.border": Style(),
-    "markdown.h1": Style(bold=True),
-    "markdown.h2": Style(bold=True, underline=True),
-    "markdown.h3": Style(bold=True),
-    "markdown.h4": Style(bold=True, dim=True),
-    "markdown.h5": Style(underline=True),
-    "markdown.h6": Style(italic=True),
-    "markdown.h7": Style(italic=True, dim=True),
+    "markdown.h1": Style(bold=True, color="light_goldenrod1", bgcolor="slate_blue3"),
+    "markdown.h2": Style(bold=True, underline=True, color="blue"),
+    "markdown.h3": Style(bold=True, color="blue"),
+    "markdown.h4": Style(bold=True, dim=True, color="blue"),
+    "markdown.h5": Style(underline=True, color="blue"),
+    "markdown.h6": Style(italic=True, color="blue"),
+    "markdown.h7": Style(italic=True, dim=True, color="blue"),
     "markdown.link": Style(color="bright_blue"),
     "markdown.link_url": Style(color="blue", underline=True),
     "markdown.s": Style(strike=True),
diff --git c/rich/markdown.py w/rich/markdown.py
index 12496487..86528411 100644
--- c/rich/markdown.py
+++ w/rich/markdown.py
@@ -143,20 +143,9 @@ class Heading(TextElement):
     def __rich_console__(
         self, console: Console, options: ConsoleOptions
     ) -> RenderResult:
-        text = self.text
-        text.justify = "center"
         if self.tag == "h1":
-            # Draw a border around h1s
-            yield Panel(
-                text,
-                box=box.HEAVY,
-                style="markdown.h1.border",
-            )
-        else:
-            # Styled text for h2 and beyond
-            if self.tag == "h2":
-                yield Text("")
-            yield text
+            yield Text("")
+        yield self.text
 
 
 class CodeBlock(TextElement):

I also personally wouldn't mind including the hash marks in the output like glow or bat do, that would help people who can't see color well or turn it off in the shell