Hi, as a fresh Reddit refugee, thanks for inviting me to expand on my view instead of meeting me with a self-righteous tirade! That knee-jerk hostility is the kind of behavior I am trying to get away from.
The first thing I should probably break down is that to me, there are important distinctions between "left" and "Democrat".
In that vein, the first thing to note about Bernie Sanders is that before running as a Democrat, he was the longest serving Independent member of Congress in the history of the United States. Just like any number of people who registered Democrat to vote in the most recent primary, Bernie partook of the Democratic Party in order to gain access to a discourse that has been dominated by the two party system. However, it doesn't necessarily make one a true Democrat.
So what about status-quo Democratic politics differ from the Sanders campaign? My key issues with the Democratic Party are that they have eagerly lined up behind Wall Street in support of the Neo-Liberal economic agenda, and are strongly biased towards entrenched, lifelong politicians who do not favor productive change. From my perspective, this is evidenced by the general lack of progress in most spheres of American politics during my entire life. By contrast, the post-election Sanders camp has been all about getting younger people with fresh perspectives into office, which I, as a fellow reformist, support.
As for the question of just how left Bernie leans, I'd actually like to talk about one of the major moderating influences on his politics: he is from Vermont, a relatively rural state for the East Coast. I grew up splitting a lot of time between urban and rural settings, and have come to view certain divisive political issues, such as gun control, as a largely urban vs. rural culture problem. So, I like that he is moderate on these issues because I see it as necessary to healing some of those rifts and uniting the political center.
I also support many of his Socialist leanings, if not all. Without totally going down the rabbit hole of every policy item, I think there are reasonable limits and requirements to be placed on social and economic systems. Quite a few of his proposals make sense to me on a rational, humanist level, and seem like they might actually work. So really, the matter of where his policies fall on the political spectrum doesn't even enter into it.