My only two cents here is that to some if it is obviously a bad build and needs to be removed and you either mention it to the person who built it or ask/tell them to remove it. It is often followed by numerous comments about why its not leech and why he won't remove it because of it being the "best" way to build the base. This has happened time and time again in particular with 1S1K (but not just him). He will defend his builds to no end and I have yet to see him understand or learn from more experience players (not that he is always wrong) just from what I have witnessed. At that point, who is to say what can and should be done? I guess that is when it should be brought to the forum for moderation.
I disagree on building a leech in the water tunnel to prevent access to the core, the amount of RU you get sometimes only helps the opposite team build numerous nukes and your base will get shit on nuke after nuke until you lose lol I know every map/instance is different. However, I do agree with Chisellers' post above.