Never. I’ve traveled by train but it was always commuting not point-to-point.
A few months, and that’s even considering I hardly ever leave London.
Tokyo to Nagoya and back via Shinkansen (superexpress train) for a seminar.
August 2009. From Paris to 11 towns in southern France, then up to Paris again.
Once every three or four weeks to visit friends in Cambridge, Oxford, Coventry, Reading, etc and family in Edinburgh, or go on holiday to eg Wales and other parts of England. So, really very often.
Two weeks ago: Mostar to Sarajevo (Bosnia-Herzegovina)
Just shy of a year ago. Seattle to Chicago and back.
October 2009. London to Manchester, and back again a few days later.
I went to Canterbury from London (and back) a few months ago, but I commute by rail everyday.
Rail travel in the US is stupid unless you’re in a major urban center with a commuter rail network or travelling the DC-Boston corridor. My wife once took a train from Lincoln, NE to Chicago. At the time (and maybe still) there were only two trains a day from Lincoln, one going east (to Chicago) and one going west (to Denver), and both passed through between 1am and 4am. Flying would have been faster and more convenient, although marginally more expensive.
Last December my wife and I took the train from New Jersey out to Portland, Oregon to visit my mom.
We had our own little tiny room, with a microscopic bathroom. Though many of the romantic visions of train travel we have were dispelled by harsh reality, it actually was an awesome trip and my wife has fond memories of that voyage.
A couple of times a year, when I have to go Philly to NYC HQ for work. When I’m going to NYC for myself, I take the bus, which is much cheaper.
It was the last time I was in London. Must be nearly two years now.
End of April. Shanghai to Nanjing. And then back.
Well, I took the Northlander train up to Huntsville for vacation last August.
I’m also curious about how to apply your logic to the GO train into Toronto. It’s classified as a commuter train in a metropolitan area, but I don’t ride it for my daily work commute. I often ride on the train to go into Toronto for a social evening, and then usually take the coach home to Hamilton. I presume that doesn’t count.
What about taking the train in for a full weekend convention? 
There was Wizard World in March, at the Ex grounds.
Last month - Toronto to Montreal and back on Via Rail.
Unfortunately the weekend we selected it did nothing but rain so we’ll be doing that again later this summer.
Never. Have taken the bus occasionally (like around 5 times) but even for medium-length distances I’ve either driven or flown. My mom doesn’t like to drive, so back when airlines were regulated and before the hub system we used to drive from Fredonia to Buffalo and then take a plane (!) from Buffalo to Syracuse to visit my grandparents. But we never took a train.
My dad always says I should take the car train from the Orlando area to Washington DC and then drive 6+ hours up to Rochester to see him, but it’s more expensive and takes longer even if I wouldn’t have to drive as many miles, so I either drive or fly.
Last time I was in Europe, which was maybe 12 years ago or so; we took the train between a few cities along the Italian Riviera.
For US train service, I only take it as a commuter - I use Chicago’s Metra rail service, which runs on regular train lines with diesel engines. I’ve been using it daily for over 15 years.
Last summer on vacation in England. I took the train from London to Hailsham and again from Salisbury to London.
Back in January, took Amtrak home to Boston from NYC after a trip, thought it’d be easier then the bus…Ha!
Was triple the cost of the bus and took just as long - not to say that I’m against trains (it was much less crowded and comfortable), but it just wasn’t worth the extra money.
Wouldn’t do the train again unless I could justify the cost, or if someone else was paying for it 
Would definitely look into it for travel over flying though, if I didn’t want to drive.
If I understand the OP correctly, the Bologna-Rimini and back trip I did last Sunday would be considered a “day’s commute”; it would only count if I’d stayed a night in Rimini. But I consider it a day trip, not a commute. Otherwise, last month I took the train from Bologna to Treviso in order to catch a plane to Prague (and then back).
Last time I had a multi-day trip where intercity train was my only means of transportation was in April, when I went from Bologna to Zürich and back, through Interlaken and Lucerne at first and then through Lugano on the back trip. So during the last year.