"This question shows research effort; it is useful and clear"
"This question does not show any research effort; it is unclear and not useful"
Those are the messages that appear when hovering over the voting-arrow buttons of a question. The issue I take with it is that the semi-colons seem to imply that display of research effort is synonymous with usefulness and clarity.
If they are not synonymous, I would like to request the feature of changing the semi-colon to a period.
They are not synonymous, and the semi colon is being used correctly here. The semi colon is indicating that these are two closely related independent clauses, which is correct. It is in no way saying they are synonymous with each other (or that one can replace the other), merely that they are closely connected statements. There is no need for a change to a period, as the sentence is grammatically correct, you seem to just be misunderstanding why a semicolon was used.
In general, research effort would lead to a clear and useful question, so they're related concepts. However, that's not always the case, but the concepts are generally things that will go hand in hand with each other, which is why they are in one coherent sentence using the semicolon.
