I'd note this is at a personal level and shouldn't be taken as an official response of any sort (I mean, I merely moderate here).
I kind of think the circumstances are significantly different depending on what the situation is.
Ideally our moderators are expected to set an example for other users. Now, with a network suspension or a suspension on that site itself - the factors Shog talks about here come into play.
We certainly are speculating, though hopefully not going into personal attacks. A network suspension shows poor judgement, if not bad faith, and their ability to deal with others in the context of that site could be questioned.
Now, on another site - I feel this ought to be different. We need to look at one core question: is this person a good moderator for the site?. If they're already demonstrating the core skills and engagement of a good moderator - and have a bad day, somewhere, it might not necessarily make them unsuited for the role. You might need folks mediating where the issue is, and stepping in - but it can get difficult to step back sometimes.
So - ideally, if a moderator is on hiatus, and has had such incidents in recent times - I feel it's something we need to talk about. It shouldn't be an automatic disqualifier unless the action was on the site in question or it was particularly bad.
If it's a site where the user isn't a moderator - I guess that's a matter for the site's moderation team and the CMs to consider. I don't think its my place to be the person who judges whether someone is suitable to be a mod, indirectly. I just deal with issues on my own sites.