Harvard Square emptied out all at once tonight

Nobody cares that you hang around with psychopaths.

The crowds at Secaucus were caused not by train capacity issues but because of a show of security theater.

http://www.nj.com/super-bowl/index.ssf/2014/02/sup...

The TSA had checkpoints before boarding trains to the Meadowlands, checkpoints which caused crowds that would have been a dream of anyone actually intending to cause harm.

It's complicated.

There are multiple different loading gauges for freight cars, some of which fit inside the passenger gauge, some of which don't. Thus some routes need to be preserved as "high and wide" routes, if there is a customer that requires large cars. On the commuter rail, this includes Worcester (west of Framingham), Lowell, and parts of the Haverhill and Franklin lines. The only way those lines will ever get high platforms is if either a freight bypass track is built (a la Woburn), a gauntlet track is built (unlikely - expensive and complicated), or the customers requiring oversize loads are somehow gotten rid of, and the freight railroads bought off to drop the restriction. The only way they can get away with mini-highs is because they have retractable edges, which a railroad employee has to physically retract before a wide freight car can pass.

There are also some places that won't get high platforms even if they aren't on a high and wide route because of the volume of freight traffic - sure, freight cars can pass high platforms, but they are a lot more subject to harmonic rocking and lateral motion in general, and the odds of them striking a platform are fairly high. This is not a problem for lines that see occasional freight (e.g. Eastern Route), but for lines that see multiple daily freight trains, that's too much risk of platform damage.

Freight does pass by high platforms daily (e.g. Lynn), but there are varying circumstances, many of which are out of the T's control, that make it unlikely we will ever have 100% high platforms.

Only because they've recognized out west that high and wide freight outnumbers passengers 10-1 virtually everywhere - the exact opposite scenario as in the northeast.

Thus they've settled with low platforms, and rolling stock designed for them - with doors on the lower level and stairs inside. Picture an MBTA bilevel, but instead of having the doors in the vestibules, they're in the middle of the lower level.

It's less ideal for accessibility, and boarding will always be less efficient than with high platforms, but none of those systems have anywhere near the ridership of a northeastern road, so it's not really a problem.

One final note though - high platforms aren't just an East Coast thing. Chicago has a mix (Metra Electric is high-level), Denver went with high-level, and California is going with high-level for HSR (and consequently Caltrain, plus I wouldn't be surprised if Metrolink or other operators eventually switch, at least partially, to ease the interface with CAHSR, and as they ramp up service levels and buy their own tracks).
It's more of a high ridership thing. If you look at commuter rail systems by ridership (or even better, ridership per mile), you'll notice the ones with the densest ridership are either high platform, or likely to soon transition to high platform. Denver is already #4 in the country, despite only opening last year, at 669 riders/mile. Only other ones in the top 10 that aren't high platform are Metra (which is only partial), Caltrain (which is converting to high platform), and TRE in Dallas, which is a bit of an outlier.

why would Boston Calling traffic have affected the Worcester commuter line at all? (see earlier comment)

Also, Google says it's a 25 minute walk from Harvard Stadium to the new station, which may for some be an attractive alternative to going all the way in to South Station and back out on the Red Line to Harvard.