First, my personal stance on this practice: if I'm in an anthology or magazine wherein an editor has included some of their own work, and I was paid on time and published in a timely manner ... then I could care less.
(On the other hand, if an editor is repeatedly publishing himself while my work, and that of others, languishes in his inventory, then it irks the hell out of me.)
But, again, in general: If I see that an editor has included his or her own work in their publication ... I could care less.
This does not mean that I think it's necessarily a wise thing to do; if an editor self-publishes a story, and it's not up to the quality of the tales surrounding it, it's an open invitation for what kids of all ages today call "lulz."
But ... if it is a good story, then no harm was done whatsoever.
I recognize that this view I have is an anachronism in the current publishing environment.
In part, it's because I first began playing the writing and editing game in earnest in the early '90s. Back then, it wasn't just an accepted practice, it was, in the case of anthologies, an expected practice. In the very first anthology I ever edited, back in 1995, I included a story of my own, and I included my own poetry in a Web zine for which I served as poetry editor.
When I started editing Mythic Delirium, back in '98 (ulp!), I decided not to make use of any of my own work — not out of any sense of violating social mores; I decided I just wasn't interested in using my zine as a showcase for my own writing.
That has been my personal rule since, for the most part. (It's true that some reviewers have looked askance at my Clockwork Phoenix introductions and suggested I'm sneaking in a story of my own — and it's a fair criticism — but I view myself as a ringmaster to that series, putting on a show, not just a compiler and arranger, and so I indulge. It's also my way of showing, not telling, that I want readers to pay attention to how the stories connect.)
But I confess, it rather surprised me when, in the late '00's, which is when I first noticed it, people seemed to start talking about this practice as if it were something on the level of the town councilman who abuses the municipal credit card.
Maybe that's okay. Discouraging the editor-as-self-publisher practice, making someone think twice before committing to it, probably does not one whit of harm.
But in my book (so to speak) it's just not that big a deal.
ETA for non-U.S. residents: Yes, I do actually mean I couldn't care less. Forgive my slang.