One of our moderators was last seen on the 22nd of May; it's now the 3rd of June (the same year, luckily). He's also a mod on Chem SE; he was last seen there 1 month ago. I don't want to name him, even though it's obvious, but he was a really nice and helpful guy when he was active 3 years ago (he last posted in 2015). Is he shirking a responsibility, or is this normal and acceptable?
This is just my opinion, not an official response: yes, I do think that a moderator who can't or doesn't want to participate in the site anymore should step down.
To be clear, I mean this in the sense that it would be considerate for an inactive moderator (who expects to remain inactive) to voluntarily step down. I'm not suggesting they should be forced out of the position. Having an inactive moderator doesn't really hurt the site, so I don't personally care about it enough to push for their removal.
I'd also note that moderator positions are volunteer positions, in the sense that a mod controls their own level of participation and there's no responsibility to maintain a minimum activity level (at least on this site). So if a moderator is inactive, they're not breaking any sort of official commitment by doing so.
My country is, for some unknown reason, still a monarchy. Perhaps that's the reason I feel somewhat uneasy about permanent positions. I really appreciate the time and effort Manish has put into this site, but perhaps it is time we start thinking whether it makes sense he's still a moderator. Especially because he was elected when this site had less than one tenth of the users it has today.
I'm not saying it particularly bothers me to see the diamond next to Manish' username. But, to be honest, I have never seen him take any moderational action or decision. For this reason, I cannot really say whether he is a good moderator or not. Needless to say, I have no reason to assume he is not; but the problem is that I don't have many reasons to assume he is either. And I'm not thrilled by the idea that someone I know nothing about (moderation-wise) has the privileges being a moderator entails.
Note that I am not calling for a new election (unlike OP). The active moderators we have today do an excellent job as far as I'm concerned. I am also not saying that Manish behaviour is unacceptable or something like that. He helped the site become what it is today, and we should always be thankful for that. But I don't really see the point in his staying a moderator. Perhaps this is a conversation we should have at some point.