It's hard to tell; people don't usually bother saying why they're going. But I can offer someone saying they almost left because of a single incident of mass-downvoting. And daenerys (who has since left LW) saying that mass-downvoting is discouraging her from participating much, though at that point she evidently had no plans to leave altogether.
And, over on Slate Star Codex (where there are no links to individual comments; sorry), go to this thread and search for "Because I got mod-bombed" you'll find ialdabaoth saying that's why they left LW; if you read other comments near that one you'll find a bunch of other people saying they left and/or are considering leaving because they don't like how it feels to get heavily downvoted; they aren't (I think) talking about Euginification, but if (1) it's common to be pushed away from places like LW because being heavily downvoted is unpleasant, and (2) there is someone around throwing heavy downvoting at people whose politics he doesn't like, there's an obvious conclusion to draw.
I don't know the politics (or, in several cases, the gender) of the people I'm pointing at, so I am not going to claim them as examples of "lefty and/or female LWers" specifically; but, again, if we have evidence (1) that mass-downvoting encourages people to leave and (2) that mass-downvoting is preferentially targeted at those who are lefty and/or female, then there's an obvious conclusion to draw.
[EDITED to add:] I am pretty sure I remember other people saying things like "I got mass-downvoted and it makes me feel really negative about LW and I hardly post here any more", but the above is all that a few minutes' googling turned up and more research than that seems unwarranted. Also, while looking I found this study of the impact of voting on user behaviour, which doesn't find that downvoting drives people away (but doesn't, I think, look at all at the sort of mass-downvoting LW suffers from); I am linking it here (1) because cherry-picking is bad and (2) because it's an interesting paper anyway.
And, over on Slate Star Codex (where there are no links to individual comments; sorry),
A comment's date and time is a permalink to that comment. Here's Ialdabaoth's "mod-bombed" comment.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.