Good question :'D unless you get a beta reader, it's hard to know if they understand the foreshadowing and the character traits because you have a whole baggage of context; even with the comments they might be talking about some details like they understood it like you but later down the road some lore was missed. But adding to what skicoak, you can make a Q&A and see what people ask - complex, simple, or things you thought you made clear in the comic but turns out you weren't clear enough or something else in the page distracted them from it.
You can also make extra episodes, tiny strips, things that don't need action and story at all times to just go "hey, this is how X acts in this situation" and make the reader understand them more, or explain a weird piece of lore straight up.