Install

git clone https://github.com/dickmao/emacs-subreddit.git
make -C emacs-subreddit install

Usage

M-x emacs-subreddit

From either summary or article buffers:
RET                  read comment
n                    read next comment
p                    read previous comment
r                    reply
g                    pull new posts
c                    mark all read
x                    un/show read
s                    isearch
q                    dismiss
SPC                  scroll through
T T                  un/display threaded
T H                  un/collapse threads