Not much has improved on the S-Bahn network as far as the points I mentioned in 2013 are concerned. Still no special branding, although many new trains now carry a purple livery, whereas outer suburban trains are green and white like all other VR trains. The mess of line letters has not been sorted, actually with the opening of the Airport line it got worse. These service are labelled (P) for clockwise and (I) for anti-clockwise. I hope that these letters mean something for the local population because otherwise I'd call them inappropriate. (I) when written isolatedly doesn't really have a distinctive character, and (P) on blue background and within a circle is mostly associated with a car park.
From my experience, also by writing about these systems, a combination of a letter (for the system) and a number for the route is the best option, and therefore it seems natural that even Germany's neighbouring countries like Poland, Czechia and Belgium have adopted the S1, S3 style for suburban trains. This type of designation has actually gone global, via Italy all the way to China, where new lines built as part of the metro system but reaching rather remote areas are labelled S1, S2, etc in most cities. Whereas previously, different routes had already been shown on some maps in different colours, they are now all purple. And I guess what's most confusing about these letters is that there is no distinction between regular and rush-hour services.
I find it too tiring to figure out what the difference between N, K and T is and I wonder if it makes that much difference to skip a few stations or whether it would be better just to have a regular all-day 10-minute service on the section to Kerava and drop a few letters instead. In fact, with a train at least every 5 minutes between Helsinki and Hiekkaharju, I bet that an all-stopping service at all times would be more reliable. And this is just about the northeastern leg, the mess on the western leg is similar. I can't think of any other city in the world that operates such a confusing stopping pattern, even Tokyo's private suburban railways seemed to be easier to understand. Some may say, this is a foreign visitor's problem, but although it may be no issue for regular users, I am sure it prevents many occasional users from taking these trains and they choose their car instead.