Better document breaking ToS will lead to bans

Closes #4102.

README.rst

@@ -12,6 +12,8 @@ as a user or through a bot account (bot API alternative).
 
     If you have code using Telethon before its 1.0 version, you must
     read `Compatibility and Convenience`_ to learn how to migrate.
+    As with any third-party library for Telegram, be careful not to
+    break `Telegram's ToS`_ or `Telegram can ban the account`_.
 
 What is this?
 -------------
@@ -76,6 +78,8 @@ useful information.
 .. _MTProto: https://core.telegram.org/mtproto
 .. _Telegram: https://telegram.org
 .. _Compatibility and Convenience: https://docs.telethon.dev/en/stable/misc/compatibility-and-convenience.html
+.. _Telegram's ToS: https://core.telegram.org/api/terms
+.. _Telegram can ban the account: https://docs.telethon.dev/en/stable/quick-references/faq.html#my-account-was-deleted-limited-when-using-the-library
 .. _Read The Docs: https://docs.telethon.dev
 
 .. |logo| image:: logo.svg

readthedocs/quick-references/faq.rst

@@ -60,6 +60,16 @@ And except them as such:
 My account was deleted/limited when using the library
 =====================================================
 
+First and foremost, **this is not a problem exclusive to Telethon.
+Any third-party library is prone to cause the accounts to appear banned.**
+Even official applications can make Telegram ban an account under certain
+circumstances. Third-party libraries such as Telethon are a lot easier to
+use, and as such, they are misused to spam, which causes Telegram to learn
+certain patterns and ban suspicious activity.
+
+There is no point in Telethon trying to circumvent this. Even if it succeeded,
+spammers would then abuse the library again, and the cycle would repeat.
+
 The library will only do things that you tell it to do. If you use
 the library with bad intentions, Telegram will hopefully ban you.
 
@@ -75,6 +85,16 @@ would fail. To solve these connection problems, you should use a proxy.
 Telegram may also ban virtual (VoIP) phone numbers,
 as again, they're likely to be used for spam.
 
+More recently (year 2023 onwards), Telegram has started putting a lot more
+measures to prevent spam (with even additions such as anonymous participants
+in groups or the inability to fetch group members at all). This means some
+of the anti-spam measures have gotten more aggressive.
+
+The recommendation has usually been to use the library only on well-established
+accounts (and not an account you just created), and to not perform actions that
+could be seen as abuse. Telegram decides what those actions are, and they're
+free to change how they operate at any time.
+
 If you want to check if your account has been limited,
 simply send a private message to `@SpamBot`_ through Telegram itself.
 You should notice this by getting errors like ``PeerFloodError``,

telethon/client/auth.py

@@ -238,13 +238,14 @@ async def _start(
                 me = await self.sign_in(phone=phone, password=password)
 
         # We won't reach here if any step failed (exit by exception)
-        signed, name = 'Signed in successfully as', utils.get_display_name(me)
+        signed, name = 'Signed in successfully as ', utils.get_display_name(me)
+        tos = '; remember to not break the ToS or you will risk an account ban!'
         try:
-            print(signed, name)
+            print(signed, name, tos, sep='')
         except UnicodeEncodeError:
             # Some terminals don't support certain characters
             print(signed, name.encode('utf-8', errors='ignore')
-                              .decode('ascii', errors='ignore'))
+                              .decode('ascii', errors='ignore'), tos, sep='')
 
         return self