despamify.py

def despamify(text: str, threshold=5) -> tuple[bool, str]:
  last_char = ""
  repeat_count = 0
  despammed = False
  output = ""
  
  for char in text:
    if char == last_char:
      repeat_count += 1
    else:
      repeat_count = 0
    
    if repeat_count < threshold:
      output += char
    else:
      despammed = True
    
    last_char = char
  
  return despammed, output

Some examples:

despamify('Hello')  # (False, 'Hello')
despamify('Hellooooo')  # (False, 'Hellooooo')
despamify('Helloooooo')  # (True, 'Hellooooo')
despamify('Whhhhhhhereees my wooooood')  # (True, 'Whhhhhereees my woooood’)
despamify('Hello!!!!!', 3)  # (True, 'Hello!!!')

If you really want to use regular expressions though, you can, with something like this:

re.sub(r'(.)\1{5,}', r'\1\1\1\1\1', 'aaaaaabaaaaaa')  # 'aaaaabaaaaa'

may or may not have spent like 10 minutes debugging to save a few seconds of reading the documentation while making that... :D