Sorry, I haven't seen that discussion, so I will just try to put down how it works, hopefully, that would answer your questions.
Basically, there are currently two factors affecting building construction speed, one being a bonus provided by huts and houses in the town, and the second one a penalty, which comes from town's population. Also, although it might be somewhat surprising, the population generated by huts themselves, doesn't count here.
As an example: in my town of Lightning Spire I have 15 level 5 Houses, each having 4 in population and yielding a 15% building time reduction. That gives us in total 15*15 = -225% building time reduction. The population of the town is 339, subtracting 15*4=60 (population generated by houses themselves) results in 339-60= +279% penalty. Now adding this two effects we get a final modifier, which appears to be 279-225= +54%.
Now let us check how it works for an individual building. The base time of construction of Colosseum is 537 seconds. After the penalty is applied that results in 537*1.54 = approx. 826 seconds = 13 minutes 46 seconds, which is just the time I would see in the game if I ordered the construction of it.
It should be also noted that there is a limit on how far you can go in accelerating construction with huts: the final reduction cannot fall below -80%, which corresponds to 5x speed up.
Please note, that all the above is a current state of matters, and, of course, may change in future.
