I'm referring to the article on Triangular Distribution, under the sub-heading: Distribution of the sum of two standard uniform variables.
Surely the maximum of sum of two uniform random numbers is not $1$. So $b$ needs to be $2$ and $c$ needs to be $1$ in the article. Am I missing something? I came across that article while writing my answer to this question, which has the correct solution.
The wiki page currently defines $X = \frac{X_1+X_2}{2}$ where $X_1,X_2$ are uniform on $[0,1]$, so $X$ is the mean, not the sum.
Maybe you're just arguing against the title of that subsection? It's entirely possible that it's a result of wikipedia having multiple authors.