I added the "for me" qualifier for a reason, mind I have a pretty good folder (Dahon Mu SL) and although I like the little bike and feel quite cool on it, I still replaced it with a full-size bike once I realized my commute doesn't need train-stashing per se.

I had similar doubts about leaving the bike in the train station parking lot. I resolved them by taking up a theft and vandalism insurance on my new commuter MTB. $200 deductible on theft means that after 3 months of ownership, they're doing me a favour by stealing it. $50 deductible on vandalism may be a bit annoying when someone would decide to steal my saddle, but so far they haven't. I park it in the most visible spot possible, to shift the risk from vandalism to theft.

I don't mean to bash folders, they definitely can be used for this kind of distances without problems, but I think in objective terms it's a lot of compromise to avoid the parking problem.