The anon got it wrong. These are ">" or "greater than" symbols, not arrows, although they look like arrowheads. They are used to signal a quote, which makes the text green on 4chan or inside a quote block on other platforms. In 4chan culture, the resulting greentext is not a quote, it has a meaning of its own.
The actual implication arrow, used in mathematical logic for statements like "if A, then B" or "A implies B", is "⇒" or "rightwards double arrow" in Unicode. Using ASCII characters, it can be written as "=>".
I know that these stories are often accused of being fake, but I guess I don't understand the context of the response. It seems like the responder is saying "go to the doctor regardless of whether you actually have a problem requiring a doctor." Which I guess could be good advice in some circumstances, but ... Maybe I'm just taking things too literally.