Normal defecation is initiated by three components
(1) spontaneous phasic contractions of rectum starting during filling.
(2) smooth muscle relaxation of the anal canal with an increased
(3) application of voluntary expulsive force as straining.
Process of Defecation: Research shows that the defecation is a complex, learned process ...
As pointed out by @KonradRudolph, this is only a partial answer. It addresses sexually-transmitted diseases, but not others. It needs further additions or a companion answer to properly address the question.
Before we can point to the evidence that covers help, we need some evidence that there is any problem to solve.
In a Salon article, Mary Roach ...
In the US and Canada, if you buy wipes which say "Flushable" on the package, you normally should never flush them. (Source.) If you do, they may clog your pipes or your local sewer / septic system. And a sewer clog may cause sewage to seep into your basement. (Source.)
Instead of flushing wipes down the toilet, you can use unscented baby wipes. ...
Specifically, if tree roots are incurring the sewer pipes, toilet tissue can become snagged on the incurring roots and can cause a blockage. This is apparently one of the most common causes of blockages.
Tree root incursion is particularly bad in areas with cracked or porous ceramic pipes, where moisture and vapours can escape into the soil, which ...
As a french, I can tell you that there is no correlation between "squat toilet" and "birth complications" in France.
Squat toilets are only found in public area. At home or work, nobody would want a "squat toilet" (only some old houses have them).
The only reason there is "squat toilet" in France, is that it's easier to clean and less water use.
And of ...
Well, according to the Mythbusters, your toothbrush is in danger no matter where you keep it.
Every time you flush a toilet, it releases an aerosol spray of tiny
tainted water droplets. [...] At the end of the month-long trial, they
sent their toothbrush collection to a microbiologist for bacterial
testing. Astonishingly, all the toothbrushes were ...
This website from ThamesWater (a water management company in UK) states that they are not flushable, and even shows you why.
Other sources tell the same story:
It's a fake.
gomerblog.com's own disclaimer states:
Gomerblog.com is strictly a satirical and fake news blog site. All articles are fake and not intended to diagnosis medical
conditions or to give medical advice. Please see a real medical
website or your doctor for diagnosis and any medical advice. Please
don’t take any advice from our website....
There are lots of links on wikipedia regarding this topic ...
Furthermore, injuries are frequently sustained by people who stand on
toilet seats to reach a height, and slip
Toilet-related injuries and deaths
Death can occur if the fecal impaction is not promptly relieved through defecation since the condition can lead to colonic perforation (hole that develops through the wall of the small intestine, large bowel), peritonitis (inflammation of the peritoneum which is a thin tissue that lines the inner wall of the abdomen and covers most of the abdominal organs), ...
In the context of the scenario you describe, yes. "Splashing onto the floor" is reduced because:
Splash-back lands on you instead, and is absorbed
As with many things, your aim "becomes more accurate with decreasing distance to the target"
Where did the 80% claim come from?
According to the 2009 NPR article There's A Fly In My Urinal:
When flies were introduced at Schiphol Airport, spillage rates dropped 80 percent, says manager Aad Keiboom
See also the 13 May 1997 Santa Cruz Sentinel:
Just visit the men's room. The tile under the urinals in the Arrivals Building has that ...