Why a regex?

mystring = mystring.replace(",", "")

is enough.

Of course, if you insist:

mystring = re.sub(",", "", mystring)

but that's probably an order of magnitude slower.

The pattern you use, ([\w],[\s\w|\w]), is consuming a word char (= an alphanumeric or an underscore, [\w]) before a ,, then matches the comma, and then matches (and again, consumes) 1 character - a whitespace, a word character, or a literal | (as inside the character class, the pipe character is considered a literal pipe symbol, not alternation operator).

So, the main problem is that \w matches both letters and digits.

You can actually leverage lookarounds:

(?<=[a-zA-Z]),(?=[a-zA-Z\s])

See the regex demo

The (?<=[a-zA-Z]) is a positive lookbehind that requires a letter to be right before the , and (?=[a-zA-Z\s]) is a positive lookahead that requires a letter or whitespace to be present right after the comma.

Here is a Python demo:

import re
p = re.compile(r'(?<=[a-zA-Z]),(?=[a-zA-Z\s])')
test_str = "2015,1674,240/09,PEOPLE V. MICHAEL JORDAN,15,15\n2015,2135,602832/09,DOYLE V ICON, LLC,15,15"
result = p.sub("", test_str)
print(result)

If you still want to use \w, you can exclude digits and underscore from it using an opposite class \W inside a negated character class:

(?<=[^\W\d_]),(?=[^\W\d_]|\s)

See another regex demo

Replace them:

posts[0].replace(',', '')

Or use the locale module (if your locale's thousands delimiter is a comma):

import locale

locale.setlocale(locale.LC_ALL, '')
n = locale.atoi(posts[0])

I would advise against using just regex for scraping. Unless Posts: (.*?) is all you're after, parse the HTML with a HTML parser like lxml or BeautifulSoup.

To remove the leading and trailing spaces you can use .strip(), and then to replace consecutive whitespace characters using the regular expression \s+:

>>> import re
>>> s = " 2.4       -2.0           4.3"
>>> re.sub("\s+", ",", s.strip())
'2.4,-2.0,4.3'

On a string you can replace any character, such as ,, like so:

s = "Hi, I'm a string"
s_new = s.replace(",", "")

Also, the comparisons you are doing on the strings may not always perform the way you expect. It may be better to cast to numeric values first. Something like:

for word in split:
    n = float(word.replace(",", ""))
    # do comparison on n, like
    # if n >= 0: ...

As a tip, try reading in your file with with:

# ...
with open(fileName, 'r') as f:
    for line in f:
        # this will give you `line` as a string 
        # ending in '\n' (if it there is an endline)
        string_wo_commas = line.replace(",", "")
        # Do more stuff to the string, like cast to float and comparisons...

This is a more idiomatic way to read in a file and do something to each line.