@Elke, kudos on 13 years of experience on THS and for a wonderfully thoughtful question.
We have been amazed at the high diversity within the housesitter community - in terms of personal situation, listing preferences and housesitting objectives.
Re your Q - suspect that there is no single answer. Local housesitters may have significantly different “wow” factors to international housesitters. We love it when Pet Parents seek to engage with us as people - not as staff; when they prepare house and welcome us in manner similar to family or friend - not as staff; and when they make effort towards us enjoying the experience and/or local area. Specifics don’t really matter but the attitude is palpable. If you make reasonable effort to be thoughtful to housesitters then it seems disappointing if they were unappreciative.
More broadly, there’s some collective ideas from THS Forum community in an earlier post on ‘green flags’.