I'm trying to book reservations online at trenitalia.com. For express night routes, I have the option of choosing different types of sleeping accomodations. But when I try to make ICN reservations, the only option is to pick which seat out of six in the compartment I want. Do all these six-seat ICN compartments change into berths, or am I missing something here?

You must determine from the website whether the particular ICN train of interest to you also has couchette service and/or wagon lits. This information should appear as part of the fares information (the fares vary according to accommodation requested). It is possible that this particular ICN train has ONLY first and second class seats, and no couchettes.

The newer "comfort class" couchettes (four per compartment, rather than six) now have dedicated railcars.

Certainly not all six-seat compartments convert into couchettes, which is why you must be certain about what accommodations this particular ICN train offers.

It seems to be just seats on the routes I'm looking at (Salerno-Palermo and Taormina-Rome).

Thanks.

Are you looking at the Conca d'Oro which departs Rome Termini at 23:00? If so, it also has "Excelsior Class" luxury wagon lits, but ONLY between Rome and Palermo. From Salerno and Taormina, there are only regular pivoting seats. If you want couchettes or regular wagon lits, you must select one of the Espresso (EXP) trains on these routes.

No, definitely Salerno and Taormina, which just have seats-only ICN and express night trains with sleepers.

Think I'll go buy a sheet.