I would say that. I don't want to hear "thank you" -- I just want a clear bug report. "Thank you" often comes across as disgenuine, a plea to try to raise the priority of the bug.
I don't really know if it effects me in a major way, but if it even effects me at all, it probably would make me less likely to want to fix a bug.
Wow. I always say thank you and have never meant what you think, and it has never even crossed my mind that it could be read that way. I doubt it means what you think very often.
In a team I worked in many years ago, there was a general consensus that a manager saying "thanks" didn't come across well. It implied that the dev was doing a favour for that person and wanted to do so. Instead, they preferred something along the lines of "good work" or "great job" or similar. This indicated that the work was of value.
This was in person and in a single company, so is a bit different from issues raised by a stranger over the internet in a bug tracker.
Personally, if I don't know the person I say/write "thanks" because I mean it, especially if it's an open source project.
I don't really know if it effects me in a major way, but if it even effects me at all, it probably would make me less likely to want to fix a bug.