Easily communicated in a "ceteris paribus, having communicated my evidence across teh internets, if you had the same priors I do, just by you reading my description of the evidence you'd update similarly as I did when perceiving the evidence first hand", yea that would be a tall order.

However, all evidence can at least be broadly categorized / circumscribed.

Consider: "I have strong evidence for my opinion which I do not present, since I cannot easily communicate it over a forum anyways" would be a copout, in that same sentence (119 characters) one could have said "My strong evidence partly consists of a perception of divine influence, when I felt the truth rather than deduced it." (117 letters) - or whatever else may be the case. That would have informed the readers greatly, and appropriately steered the rest of the conversation.

If someone had a P=NP proof / a "sophisticated" (tm) qualia theory, he probably wouldn't fully present it in a comment. However, there is a lot that could be said meaningfully (an abstract, a sketch, concepts drawn upon), which would inform the conversation and move it along constructively.

"What strong evidence do you already posses (sic) that leads you to believe this thing" is a valid question, and generally deserves at least a pointer as an answer, even when a high fidelity reproduction of the evidence qua fora isn't feasible.