diff --git i/test/unit/lib/redmine/wiki_formatting/macros_test.rb w/test/unit/lib/redmine/wiki_formatting/macros_test.rb
index 8c3011575..41a7e6857 100644
--- i/test/unit/lib/redmine/wiki_formatting/macros_test.rb
+++ w/test/unit/lib/redmine/wiki_formatting/macros_test.rb
@@ -314,6 +314,97 @@ class Redmine::WikiFormatting::MacrosTest < Redmine::HelperTest
     end
   end
 
+  BLOCK_LEVEL_CONTENT_IN_PARAGRAPH_RE =
+    %r{<p(?:\s[^>]*)?>(?:(?!</p>).)*<(?:div|h[1-6]|hr|ol|pre|table|ul)[\s/>]}m
+
+  def test_macro_returning_block_level_content_should_not_be_wrapped_in_paragraph
+    text = <<~RAW
+      {{collapse(Show example, Hide example)
+      h2. Heading
+
+      Some text
+      }}
+    RAW
+    %w[textile common_mark].each do |format|
+      with_settings :text_formatting => format do
+        assert_no_match BLOCK_LEVEL_CONTENT_IN_PARAGRAPH_RE, textilizable(text)
+      end
+    end
+  end
+
+  def test_include_macro_should_not_be_wrapped_in_paragraph
+    @project = Project.find(1)
+    %w[textile common_mark].each do |format|
+      with_settings :text_formatting => format do
+        assert_no_match BLOCK_LEVEL_CONTENT_IN_PARAGRAPH_RE, textilizable('{{include(Another page)}}')
+      end
+    end
+  end
+
+  # Example 1 of #43730: text between collapses in the same paragraph
+  def test_macro_multiple_collapse_with_text_between_should_not_generate_block_inside_p
+    text = <<~RAW
+      1 {{collapse(1)
+      content 1
+      }}
+      2 {{collapse(2)
+      content 2
+      }}
+      3 {{collapse(3)
+      content 3
+      }}
+    RAW
+    with_settings :text_formatting => 'textile' do
+      assert_no_match BLOCK_LEVEL_CONTENT_IN_PARAGRAPH_RE, textilizable(text)
+    end
+  end
+
+  # Example 2 of #43730: adjacent collapses with no text between
+  def test_macro_multiple_collapse_adjacent_should_not_generate_block_inside_p
+    text = <<~RAW
+      {{collapse(1)
+      content 1
+      }}
+      {{collapse(2)
+      content 2
+      }}
+    RAW
+    with_settings :text_formatting => 'textile' do
+      assert_no_match BLOCK_LEVEL_CONTENT_IN_PARAGRAPH_RE, textilizable(text)
+    end
+  end
+
+  # Example 3 of #43730: multiple groups of collapses separated by a blank line
+  def test_macro_multiple_collapse_groups_should_not_generate_block_inside_p
+    text = <<~RAW
+      1 {{collapse(1)
+      content 1
+      }}
+      2 {{collapse(2)
+      content 2
+      }}
+
+      3 {{collapse(3)
+      content 3
+      }}
+    RAW
+    with_settings :text_formatting => 'textile' do
+      assert_no_match BLOCK_LEVEL_CONTENT_IN_PARAGRAPH_RE, textilizable(text)
+    end
+  end
+
+  def test_macro_returning_inline_content_should_keep_its_paragraph
+    with_settings :text_formatting => 'textile' do
+      assert_match %r{<p>Some text: <a}, textilizable('Some text: {{issue(1)}}')
+    end
+  end
+
+  def test_text_without_macro_should_not_be_altered
+    with_settings :text_formatting => 'textile' do
+      assert_equal '<p>Some text</p>', textilizable('Some text').strip
+    end
+  end
+
   def test_macro_child_pages
     expected =
       "<p><ul class=\"pages-hierarchy\">\n" \