diff --git a/GUI/host/textthread.cpp b/GUI/host/textthread.cpp
index c047356..40be2d1 100644
--- a/GUI/host/textthread.cpp
+++ b/GUI/host/textthread.cpp
@@ -4,6 +4,16 @@
 
 extern const wchar_t* INVALID_CODEPAGE;
 
+// return true if repetition found (see https://github.com/Artikash/Textractor/issues/40)
+static bool RemoveRepetition(std::wstring& text)
+{
+	wchar_t* end = text.data() + text.size();
+	for (int length = text.size() / 3; length > 6; --length)
+		if (memcmp(end - length * 3, end - length * 2, length * sizeof(wchar_t)) == 0 && memcmp(end - length * 3, end - length * 1, length * sizeof(wchar_t)) == 0)
+			return RemoveRepetition(text = std::wstring(end - length, length)), true;
+	return false;
+}
+
 TextThread::TextThread(ThreadParam tp, HookParam hp, std::optional<std::wstring> name) :
 	handle(threadCounter++),
 	name(name.value_or(Util::StringToWideString(hp.name).value())),
@@ -44,7 +54,7 @@ void TextThread::Push(BYTE* data, int length)
 	if (filterRepetition)
 	{
 		if (std::all_of(buffer.begin(), buffer.end(), [&](auto ch) { return repeatingChars.find(ch) != repeatingChars.end(); })) buffer.clear();
-		if (Util::RemoveRepetition(buffer)) // sentence repetition detected, which means the entire sentence has already been received
+		if (RemoveRepetition(buffer)) // sentence repetition detected, which means the entire sentence has already been received
 		{
 			repeatingChars = std::unordered_set(buffer.begin(), buffer.end());
 			AddSentence(std::move(buffer));
diff --git a/GUI/host/util.cpp b/GUI/host/util.cpp
index 0a77833..f4d92ef 100644
--- a/GUI/host/util.cpp
+++ b/GUI/host/util.cpp
@@ -310,15 +310,6 @@ namespace Util
 		return {};
 	}
 
-	bool RemoveRepetition(std::wstring& text)
-	{
-		wchar_t* end = text.data() + text.size();
-		for (int length = text.size() / 3; length > 6; --length)
-			if (memcmp(end - length * 3, end - length * 2, length * sizeof(wchar_t)) == 0 && memcmp(end - length * 3, end - length * 1, length * sizeof(wchar_t)) == 0)
-				return RemoveRepetition(text = std::wstring(end - length, length)), true;
-		return false;
-	}
-
 	std::optional<HookParam> ParseCode(std::wstring code)
 	{
 		if (code[0] == L'/') code.erase(0, 1); // legacy/AGTH compatibility
diff --git a/GUI/host/util.h b/GUI/host/util.h
index 4a0c522..9ea63d6 100644
--- a/GUI/host/util.h
+++ b/GUI/host/util.h
@@ -10,8 +10,6 @@ namespace Util
 	std::vector<std::pair<DWORD, std::optional<std::wstring>>> GetAllProcesses();
 	std::optional<std::wstring> GetClipboardText();
 	std::optional<std::wstring> StringToWideString(const std::string& text, UINT encoding = CP_UTF8);
-	// return true if repetition found (see https://github.com/Artikash/Textractor/issues/40)
-	bool RemoveRepetition(std::wstring& text);
 	std::optional<HookParam> ParseCode(std::wstring code);
 	std::wstring GenerateCode(HookParam hp, DWORD processId);
 }
diff --git a/extensions/extensionimpl.cpp b/extensions/extensionimpl.cpp
index e333bd4..8decc99 100644
--- a/extensions/extensionimpl.cpp
+++ b/extensions/extensionimpl.cpp
@@ -2,15 +2,16 @@
 
 bool ProcessSentence(std::wstring& sentence, SentenceInfo sentenceInfo);
 
-/**
-	* You shouldn't mess with this or even look at it unless you're certain you know what you're doing.
-	* Param sentence: pointer to sentence received by Textractor (UTF-16).
-	* This can be modified. Textractor uses the modified sentence for future processing and display. If empty (starts with null terminator), Textractor will destroy it.
-	* Textractor will display the sentence after all extensions have had a chance to process and/or modify it.
-	* The buffer is allocated using HeapAlloc(). If you want to make it larger, please use HeapReAlloc().
-	* Param miscInfo: pointer to array containing misc info about the sentence. End of array is marked with name being nullptr.
-	* Return value: the buffer used for the sentence. Remember to return a new pointer if HeapReAlloc() gave you one.
-	* THIS FUNCTION MAY BE RUN SEVERAL TIMES CONCURRENTLY: PLEASE ENSURE THAT IT IS THREAD SAFE!
+/*
+	You shouldn't mess with this or even look at it unless you're certain you know what you're doing.
+	Param sentence: pointer to sentence received by Textractor (UTF-16).
+	This can be modified. Textractor uses the modified sentence for future processing and display. If empty (starts with null terminator), Textractor will destroy it.
+	Textractor will display the sentence after all extensions have had a chance to process and/or modify it.
+	The buffer is allocated using HeapAlloc(). If you want to make it larger, please use HeapReAlloc().
+	Param miscInfo: pointer to array containing misc info about the sentence. End of array is marked with name being nullptr.
+	Return value: the buffer used for the sentence. Remember to return a new pointer if HeapReAlloc() gave you one.
+	This function may be run concurrently with itself: please make sure it's thread safe.
+	It will not be run concurrently with DllMain.
 */
 extern "C" __declspec(dllexport) wchar_t* OnNewSentence(wchar_t* sentence, const InfoForExtension* miscInfo)
 {
diff --git a/include/common.h b/include/common.h
index 7624635..2a73ec8 100644
--- a/include/common.h
+++ b/include/common.h
@@ -90,7 +90,7 @@ inline auto FormatArg(const std::basic_string<C>& arg) { return arg.c_str(); }
 #pragma warning(push)
 #pragma warning(disable: 4996)
 template <typename... Args>
-inline std::string FormatString(const char* format, Args... args)
+inline std::string FormatString(const char* format, const Args&... args)
 {
 	std::string buffer(snprintf(nullptr, 0, format, FormatArg(args)...), '\0');
 	sprintf(buffer.data(), format, FormatArg(args)...);
@@ -98,7 +98,7 @@ inline std::string FormatString(const char* format, Args... args)
 }
 
 template <typename... Args>
-inline std::wstring FormatString(const wchar_t* format, Args... args)
+inline std::wstring FormatString(const wchar_t* format, const Args&... args)
 {
 	std::wstring buffer(_snwprintf(nullptr, 0, format, FormatArg(args)...), L'\0');
 	_swprintf(buffer.data(), format, FormatArg(args)...);