Some posts I see here are lower quality. However, if I downvote, I'll lose reputation and lose privileges.
Is there a way for me to express my opinion on this new site without the loss of rep?
We won't lose rep on downvoting questions but lose 1 rep on downvoting answers. Don't be afraid of losing reputation when your inner says the post is of really bad quality, if you are confused whether it's considered low quality or not then you can comment on that post quoting the same.
For example, you can comment like:
Hey, I see that this answer doesn't really answer OP's question or it has some content issues that are conceptually or by whatever means wrong (provide some links if you can), I propose that it goes into low quality answer.
Can you please edit to fix X, Y or improve the answer to specifically answer the OP's question without going off-topic. I appreciate your taking your time to answer and improve on it.
By commenting so, we make sure that we are being polite and respecting the answer contributor and asking him/her to provide relevant content. Also this comment serves a sniffer to others who are going through it, if they also share the same issue as you are facing then they can also downvote it and ultimately it gets wiped off by the system.
Ask a question post a few answers. Due to Vote Early, Vote Often (Seriously) you should then have enough reputation to stomach the penalty of a few down votes.
After a while it will reach a level where you don't have to care about that reputation that much. If it's really off-topic you can always flag to close.
If the post is low quality, you've the following possibilities:
Answers: If other users share your opinion and the vote has zero or negative score, you can flag it as 'very low quality'.
This answer has severe formatting or content problems. This answer is unlikely to be salvageable through editing, and might need to be removed.
If it has positive score, it's worth to comment on the post explaining your thoughts, so the author can improve the post (you can also suggest the changes) and other users can reconsider their votes, also this may alert other users who can share your opinion.
Question: Downvotes on questions are free. You can also flag them as primarily opinion-based, off-topic or as unclear.
Either way, you should not afraid of down voting the post, because the owner of the post will lost twice as that (2 reputation). It is actually a moderation privilege, and it comes with the cost of 1 reputation which is taken away from you to avoid any abuse, so use it wisely.
See: Help Center > Privileges > Vote Down help section:
When should I vote down?
Use your downvotes whenever you encounter an egregiously sloppy, no-effort-expended post, or an answer that is clearly and perhaps dangerously incorrect.
You have a limited number of votes per day, and answer down-votes cost you a tiny bit of reputation on top of that; use them wisely.
What happens when I vote down?
When you vote down, you are nudging that content "down" the page, so it will be seen by fewer people. Voting down answers is not something we want you to take lightly, so it is not free.
- Downvotes remove 2 reputation from the post owner.
- Downvotes on answers remove 1 reputation from you, the voter.
- Downvotes on questions are free.