diff --git a/plugins/smolnet.py b/plugins/smolnet.py
index 0937e23..c571521 100644
--- a/plugins/smolnet.py
+++ b/plugins/smolnet.py
@@ -31,6 +31,8 @@ setting, and every setting has a default, so a site can switch it on with just
                                   Notes section; off by default since not
                                   every site using this plugin has been
                                   checked for footnotes
+    SMOLNET_CALLOUTS      {}          callout kind -> label, for `> [!kind]`
+                                  blocks; see rewrite_callouts
 
 Every run of links here is a **Markdown list**, which is what each format needs:
 Mews Profile reads a dated link as a feed entry only when it starts a list item
@@ -120,6 +122,9 @@ FOOTNOTE_REF = re.compile(r"\[\^([^\]]+)\]")
 # citation it was meant to carry.
 LINKREF_DEF = re.compile(r"^\[(\d+)\]:", re.MULTILINE)
 
+# The opening line of a GitHub/Obsidian-style callout, "> [!kind] title".
+CALLOUT = re.compile(r"^([ ]{0,3}>[ ]?)\[!(\w+)\][ \t]*(.*)$", re.MULTILINE)
+
 
 def rot13(text):
     """The obfuscation used on addresses in the HTML templates."""
@@ -322,6 +327,33 @@ def rewrite_footnotes(text, labels, warn):
     return body.rstrip() + "\n\n" + "\n".join(notes) + "\n"
 
 
+def rewrite_callouts(text, kinds):
+    """Turn a `> [!kind]` marker into a bold label line, leaving the rest of
+    the passage an ordinary blockquote.
+
+    The HTML build renders these as boxes (an <aside>, via a Markdown
+    extension in the site itself). gemtext has nothing to draw a box with, and
+    a quote is the one block it does set apart, so the passage stays one; only
+    the marker would otherwise print literally as "[!ontology]". Kinds not in
+    `kinds` are left alone, matching the HTML side, which also only boxes the
+    kinds it was told about.
+    """
+    if not kinds:
+        return text
+    kinds = {k.lower(): v for k, v in kinds.items()}
+
+    def sub(match):
+        kind = match.group(2).lower()
+        if kind not in kinds:
+            return match.group(0)
+        title = match.group(3).strip() or kinds[kind]
+        # The label as a paragraph of its own inside the quote, so it can't run
+        # into the passage's first sentence.
+        return "%s**%s**\n>" % (match.group(1), title)
+
+    return CALLOUT.sub(sub, text)
+
+
 def toml_escape(value):
     return str(value).replace("\\", "\\\\").replace('"', '\\"')
 
@@ -384,6 +416,7 @@ class CapsuleGenerator(Generator):
                       s.get("LOSTIMAGES_DEAD_HOSTS", [])}
         sidecar_name = s.get("SMOLNET_SIDECAR", ".itsybitsy.toml")
         footnotes = s.get("SMOLNET_FOOTNOTES", False)
+        callouts = s.get("SMOLNET_CALLOUTS", {})
         # kapara serves the same remark42 thread the HTML widget shows, over
         # Gemini, Spartan and Nex. Articles only: the widget is on articles
         # only, and a page with a thread nobody can reach from the site is a
@@ -416,6 +449,7 @@ class CapsuleGenerator(Generator):
             body = rewrite_html_links(body, urls, self._warn)
             body = reveal_rot13(body, rot_attr)
             body = drop_dead_images(body, dead_hosts)
+            body = rewrite_callouts(body, callouts)
             if footnotes:
                 body = rewrite_footnotes(body, labels, self._warn)
             # Blank lines, not newlines: a heading and the line under it are