With the car? I go by train, and then either by bike or tram. Much easier
But outside of these hours the car is simply much more convenient. I lived in Brussels for 42 years and did everything that wasn't walking distance by car (very mostly in the pre- Uber days). You simply know where the parking spots are and it's too convenient to have your own car when you come out of the restaurant, without to have to worry about the last bus / last tram / getting mugged.
TFA's author went up early in the morning: he's dodging traffic jams.
For example FOSDEM if I'm concerned there'd be no spot? I'd park on the other side of the Bois de la Cambre and then walk to the campus.
Bicycling? It's nice when you don't have a nice bicycle. Otherwise it's gone in 60 seconds. I also don't see many people bicycling when the weather is bad and, well, let's get real: it rains a huge freaking lot in Brussels.
P.S: FOSDEM is happening in the Ixelles district, adjacent to the Uccle district (the Bois de la Cambre is on both districts). These are the two poshest, classiest, most expensive districts of Brussels with very few high-rises and very few soviet-style buildings with lots of apartments (these exists but in other districts). It's as if FOSDEM was taking place in Beverly Hills. In these posh areas there are parking spots.