How much reputation does a steam user have?
Python 3, 73 bytes

I'm sure this answer is garbage and will be beaten soon, but there's no other python answers yet

lambda x:sum(["- +".index(i[0])-1for i in x.split('\n')if i[1:4]=="rep"])


Use like this:

f = lambda x:sum(["- +".index(i[0])-1for i in x.split('\n')if i[1:4]=="rep"])
print(f("PUT INPUT HERE"))




Fetching from steam

Here's some sample code which fetches the first 100 comments from KennyS' profile and calculates his rep.

import requests
from bs4 import BeautifulSoup

# Kenny's profile as Steam ID 64
# You can adjust this to whatever numbers you want
STEAM_PROFILE_URL = "76561198024905796"
payload =  {"start" : 0, "count" : 100}
r = requests.post("http://steamcommunity.com/comment/Profile/render/{}/-1/".format(STEAM_PROFILE_URL), payload)

# Comments are html inside a json object
soup = BeautifulSoup(r.json()["comments_html"], "html.parser")

# Get raw text for every comment.
# The " ".join() strips out the newlines and tabs which are part of html
comments = [" ".join(s.text.split()) for s in soup.find_all("div", {"class" : "commentthread_comment_text"})]

calculateRep = lambda x:sum(["- +".index(i[0])-1for i in x.split('\n')if i[1:4]=="rep"])

print(calculateRep("\n".join(comments)))