bxl-forever
We discussed this point at the Belgian OSM meeting tonight.

place=neighbourhood should be avoided in large cities.  Here are the primary reasons:
1) The boundaries are never defined properly (unless very specific examples such as Usquare, enclosed within a few walls).
2) Not everyone has the same understanding of what qualifies as a neighbourhood.  Even the name differs for some people.
3) Finally, the purpose.  Is it to have some more names stand out on the map?  Is it intended that people could search a name and get where it is? → In that latter case the search function already brings enough results when people type "Dansaert", "Porte de Ninove - Ninoofsepoort", "Schuman" or other neighbourhoods in similar notes.

It was a good question but after considering the point we felt it would not do any good adding those for the time being.