The ideas of uncertainty as a quantifiable attribute and statistical significance of results are among the most important concepts of all fields of science and technology. Hence, we may find related questions on several sites. Depending on the particular problem, some questions may even find better answers on other sites than on Chemistry Stack Exchange. However, the fact that a question is on topic on another site does not make it off topic on Chemistry. (Also note that, in most cases, other sites don’t migrate questions to Chemistry even if they could find better answers here.)
The basic principles of the manifold rules and guidelines concerning uncertainty found in all fields of science and technology today are actually quite similar. Arguably the best references for these basic principles are the famous Guide to the expression of uncertainty in measurement (GUM) and the International vocabulary of metrology (VIM). These guides are published by BIPM, IEC, IFCC, ILAC, ISO, IUPAC, IUPAP, and OIML, which illustrates the international consensus on this topic.
The concept of significant digits is just a simplified form of the concept of uncertainty; however, it is ubiquitous in chemistry. A number is considered to lie within the error limits of the last significant digit(s). When a number is given without any further information, it is generally interpreted so that the last digit is rounded with a rounding range equal to 1 in the last digit. It essential that everyone understands this concept, and it is no surprise that we receive questions relating to this topic.
Of course, working with the concept of significant digits is only mathematics. However, all quantity calculus is merely performing mathematical operations on quantities. Following this reasoning, we could migrate all questions relating to physical chemistry or similar fields to Mathematics Stack Exchange since all of these questions are actually mathematics. The reason for this is that mathematics is the language in which we write such questions and answers. We might just as well migrate all questions to English Language & Usage Stack Exchange since the texts of all questions are written in English.