I encourage using screenshots for toots you disagree with or don't want to spread around the #fediverse.
But using them for things you actually agree with without providing a link is just wrong and undermines the whole concept of this network.
A simple reply is enough for your followers to find the original post/context.
Your opinion should be part of the conversation, not just a tool for self-promotion.
I think this highlights the role of #QT in being part of the #conversation, as it not only encourages the explicit link back to the source content, but it presents the context without requiring the follower to jump through the extra step, breaking their flow to go and find that context.
I would say that I'll always discourage screenshots. Not only does it break the link of the conversation, but using images to present text has accessibility and efficiency issues.
Part of what makes conversations valuable is seeing even the stuff a person disagrees with. If a conversation isn't worth spreading at all, then it's probably not worth replying to anyway.
Like you said, part of conversation, not just self-promotion, but that applies to promoting your own side at the exclusion of the other as well.
