This page lists Wikipedia pages by the total amount of text in all of their talk page archives put together. It is the best measure there is for determining how much squabbling has gone on behind the scenes for a given page.
Here is a ranking of all 63 of the listed pages that are actual articles (as opposed to policy/administrative/user pages), in descending order:
Donald Trump
Intelligent design
Climate change
Barack Obama
United States
Jesus
Race and intelligence
Catholic Church
Circumcision
Homeopathy
Muhammad
Gamergate (harassment campaign)
Chiropractic
Abortion
Monty Hall problem
Gaza War (2008-2009)
Evolution
Prem Rawat
Sarah Palin
India
Israel
World War II
Christ myth theory
Mass killings under communist regimes
Jehovah's Witnesses
September 11 attacks
Cold fusion
Climatic Research Unit email controversy
Armenian genocide
Anarchism
Atheism
Falun Gong
Neuro-linguistic programming
Jerusalem
Control of cities during the Syrian civil war
Kosovo
British Isles
Transcendental Meditation
United Kingdom
George W. Bush
Christianity
COVID-19 pandemic
Libertarianism
Acupuncture
Thomas Jefferson
International recognition of Kosovo
Israel and apartheid
Adolf Hitler
United States and state terrorism
Syrian civil war
List of best-selling music artists
Julian Assange
Russo-Georgian War
Historicity of Jesus
Second Amendment to the United States Constitution
Tea Party movement
List of common misconceptions
Murder of Meredith Kercher
Genesis creation narrative
Taiwan
Hillary Clinton
Electronic cigarette
Michael Jackson
Bubbling under (present in earlier versions; I have gone back to 2015 so far here, though the page history goes back to 2010):
0.999...
European Union
Chronic fatigue syndrome
Russian interference in the 2016 United States elections
Shakespeare authorship question
Fascism
Astrology
The Holocaust
Joseph Smith
Chelsea Manning
List of scientists who disagree with the scientific consensus on global warming [NOTE: now deleted]
Really not sure where there can be any controversy.
Israel
How could a page about a math problem end up more controversial there than a page on Pissrael?
0.999...
This is hilarious. How is this in any way controversial? Every person who diligently studies calculus for just a few weeks understands that 0.999... = 1, and why.
You need to prove that 0.333... is, indeed, 1/3 (and also that 0.999... = 0.333...*3) for that. Without being familiar with any sort of construction of real numbers, i.e. without understanding what real numbers are, you are just going to be doing a lot of hand-waving.
But yes, if one already accepts that 0.333... = 1/3, then that proof works. However, if one understands the reasons why 0.333... = 1/3, there are easier ways to prove that 0.999... = 1. Or, rather, why 0.999... = 1 is obvious to such people.
And sure, one might be familiar with any of those constructions without studying calculus, but if one does study calculus, they are going to study what real numbers are.
Also, fun fact for the onlookers: every repeating decimal represents a rational number, and every rational number can be represented by up to two repeating decimals (counting terminating decimals as repeating here). This can be generalised to natural bases other than 10, as well. Furthermore, if you have a repeating decimal that represents some rational number x, such that -1 <= x <= 1, then x = p/10n+x/10n, where p is some integer and n is a natural number, from where it follows that x = p/(10n-1).
Some examples:
-0.999... = 9/10+0.999.../10 => 0.999... = 9/(10-1) = 9/9 = 1
-0.123123123... = 123/103+123123123.../103 => 0.123123123... = 123/(103-1) = 123/999
More generally, when working with other natural bases, we have (x = p/bn+x/bn) => (x = p/(bn-1)), where b is the base. As such, 0.111... (base 2) = 1/10+0.111.../10 (base 2) => 0.111... (base 2) = 1/(10-1) (base 2) = 1/1 = 1.
Yeah 1/3 being periodic is just an artifact of using base 10, because 10 isn’t evenly divisible by 3. If you use say base 60 as the Babylonian did then the artifact vanishes.
Yes repeating happens in every base because every base has integers not evenly divisible by its base. Whether a fraction repeats is a particularity of which base is chosen to represent it.