[Ibrîniðilpathânezel]

No imminent danger exists? At this point, they do not know what became of all of the Nazgul, who are at their most dangerous when they are unclad. Frodo should not have survived his wounding with the Morgul knife, and though he did, can anyone in Rivendell say precisely WHY he did not? Do they yet know for certain that this is simply because of Frodo's "hobbit tenacity," or because of some design of the Ring itself? And there is the very imminent and immediate danger in the very presence of that Ring in Rivendell. Gandalf we know has felt its pull, and though he has refused it, does not trust himself to touch it again -- do we know how others would fare in the presence of that danger? We know that it was in Rivendell that Boromir first saw the Ring and began to desire it -- who else might have felt that same desire? The very presence of the Ring is a terrible danger, and to make light of it is potentially offering an invitation for it to start looking for a new bearer in the person who might not consider it dangerous, and would not be so careful in protecting it. In my opinion, Gandalf is not being a wet blanket because he is a gloomy, snarky person; he is demonstrating concern for Pippin, because of his affection for him. It is noted by Tolkien that one of Gandalf's shortcomings is a quick temper for the rebuking of folly, and after spending a good long while as Saruman's prisoner because of Saruman's lust for the Ring (a thing that he, unlike Pippin, has never seen nor even been its presence), any apparent flippancy regarding the Ring would likely seem to him the worst of folly. I believe that Gandalf acts as he does because he fears for the hobbits, who are comparatively young and inexperienced, and he feels it is better to risk getting a reputation as someone gloomy and grumpy than it is to let them (or anyone, for that matter) treat too lightly something that is a danger to their entire world. They may be sitting in a fortress inside Rivendell, but in bringing the Ring within that fortress, they have brought with them the very heart of their enemy -- and it would be best not to stir that heart unnecessarily. IMHO, of course.