diff --git a/isort/output.py b/isort/output.py
index ce687ff27..cf6e49684 100644
--- a/isort/output.py
+++ b/isort/output.py
@@ -1,7 +1,7 @@
 import copy
 import itertools
 from functools import partial
-from typing import Iterable, List, Tuple
+from typing import Dict, Iterable, List, Tuple
 
 from isort.format import format_simplified
 
@@ -57,9 +57,6 @@ def sorted_imports(
             from_modules, key=lambda key: sorting.module_key(key, config, section_name=section)
         )
 
-        if config.force_sort_within_sections:
-            copied_comments = copy.deepcopy(parsed.categorized_comments)
-
         section_output: List[str] = []
         if config.from_first:
             section_output = _with_from_imports(
@@ -107,11 +104,20 @@ def sorted_imports(
             )
 
         if config.force_sort_within_sections:
-            # Remove comments
-            section_output = [line for line in section_output if not line.startswith("#")]
+            # collapse comments
+            comments_above = []
+            new_section_output: List[str] = []
+            for line in section_output:
+                if line.startswith("#"):
+                    comments_above.append(line)
+                elif comments_above:
+                    new_section_output.append(_LineWithComments(line, comments_above))
+                    comments_above = []
+                else:
+                    new_section_output.append(line)
 
-            section_output = sorting.naturally(
-                section_output,
+            new_section_output = sorting.naturally(
+                new_section_output,
                 key=partial(
                     sorting.section_key,
                     order_by_type=config.order_by_type,
@@ -121,19 +127,11 @@ def sorted_imports(
                 ),
             )
 
-            # Add comments back
-            all_comments = copied_comments["above"]["from"]
-            all_comments.update(copied_comments["above"]["straight"])
-            comment_indexes = {}
-            for module, comment_list in all_comments.items():
-                for idx, line in enumerate(section_output):
-                    if module in line:
-                        comment_indexes[idx] = comment_list
-            added = 0
-            for idx, comment_list in comment_indexes.items():
-                for comment in comment_list:
-                    section_output.insert(idx + added, comment)
-                    added += 1
+            # uncollapse comments
+            section_output = []
+            for line in new_section_output:
+                section_output.extend(getattr(line, "comments", ()))
+                section_output.append(str(line))
 
         section_name = section
         no_lines_before = section_name in config.no_lines_before
@@ -535,3 +533,9 @@ def _normalize_empty_lines(lines: List[str]) -> List[str]:
 
     lines.append("")
     return lines
+
+
+class _LineWithComments(str):
+    def __new__(cls, value, comments):
+        cls.comments = comments
+        return super().__new__(cls, value)  # type: ignore
diff --git a/scripts/build_config_option_docs.py b/scripts/build_config_option_docs.py
index a1d43f43a..927c858b4 100755
--- a/scripts/build_config_option_docs.py
+++ b/scripts/build_config_option_docs.py
@@ -170,7 +170,7 @@ def config_options() -> Generator[ConfigOption, None, None]:
             extra_kwargs["description"] = cli.help
 
         yield ConfigOption(
-            name=name, default=cli.default, cli_options=cli.option_strings, **extra_kwargs,
+            name=name, default=cli.default, cli_options=cli.option_strings, **extra_kwargs
         )
 
 
diff --git a/tests/test_isort.py b/tests/test_isort.py
index 4ef2a0a92..94fea3d70 100644
--- a/tests/test_isort.py
+++ b/tests/test_isort.py
@@ -4087,25 +4087,6 @@ def test_isort_ensures_blank_line_between_import_and_comment() -> None:
     assert api.sort_code_string(test_input, **config) == expected_output
 
 
-def test_moving_comments_issue_726():
-    config = {"force_sort_within_sections": 1}  # type: Dict[str, Any]
-    test_input = (
-        "from Blue import models as BlueModels\n"
-        "# comment for PlaidModel\n"
-        "from Plaid.models import PlaidModel\n"
-    )
-    assert api.sort_code_string(test_input, **config) == test_input
-
-    test_input = (
-        "# comment for BlueModels\n"
-        "from Blue import models as BlueModels\n"
-        "# comment for PlaidModel\n"
-        "# another comment for PlaidModel\n"
-        "from Plaid.models import PlaidModel\n"
-    )
-    assert api.sort_code_string(test_input, **config) == test_input
-
-
 def test_pyi_formatting_issue_942(tmpdir) -> None:
     test_input = "import os\n\n\ndef my_method():\n"
     expected_py_output = test_input.splitlines()
diff --git a/tests/test_regressions.py b/tests/test_regressions.py
new file mode 100644
index 000000000..eb141663e
--- /dev/null
+++ b/tests/test_regressions.py
@@ -0,0 +1,38 @@
+"""A growing set of tests designed to ensure isort doesn't have regressions in new versions"""
+import isort
+
+
+def test_isort_duplicating_comments_issue_1264():
+    """Ensure isort doesn't duplicate comments when force_sort_within_sections is set to `True`
+    as was the case in issue #1264: https://github.com/timothycrosley/isort/issues/1264
+    """
+    assert (
+        isort.code(
+            """
+from homeassistant.util.logging import catch_log_exception
+
+# Loading the config flow...
+from . import config_flow
+""",
+            force_sort_within_sections=True,
+        ).count("# Loading the config flow...")
+        == 1
+    )
+
+
+def test_moving_comments_issue_726():
+    test_input = (
+        "from Blue import models as BlueModels\n"
+        "# comment for PlaidModel\n"
+        "from Plaid.models import PlaidModel\n"
+    )
+    assert isort.code(test_input, force_sort_within_sections=True) == test_input
+
+    test_input = (
+        "# comment for BlueModels\n"
+        "from Blue import models as BlueModels\n"
+        "# comment for PlaidModel\n"
+        "# another comment for PlaidModel\n"
+        "from Plaid.models import PlaidModel\n"
+    )
+    assert isort.code(test_input, force_sort_within_sections=True) == test_input