There are four separate pinned topics for completed games on different engines. Would it not be cleaner to simply have one topic with four sections, or the entire list alphabetised with the maker indicated in brackets or something?

They were that way at one time, but Harryb412 had felt they would be better separate so that people can see which maker of choice to click on right from the forum.

In most forums diffrent topics that are created by moderators, staff and other important people are sepeperated to answer diffrent questions, provide information or simply display rules. For example Forum policies and regulations may in some cases be diffrent from that paticular forums rules.

a good example is to look at global rules versuses Games under constructions rules.