I looked at the two complaints you linked to and at how those threads seem to be displayed on these users' instances:
- https://sfba.social/@otters_raft@lemmy.ca/115267196743748430
- https://mas.to/@otters_raft@lemmy.ca/115283224174559468
(edit: I don't know why they aren't displaying as links, but changing them to have a link text doesn't help either, so I'm keeping them like this)
That looks the same as it has always looked, to the best of my knowledge. I've gotten at least one similar complaint before, from a Mastodon user who didn't understand what they were looking at when they got a Lemmy post in their timeline. So I think the answer to your question is no, nothing changed, either it is a coincidence that you got two such complaints within a few days, or what actually changed is that your posts have (for whatever reason) become more visible on Mastodon.