The negatives of the feature I see are:
- (as above) Where users are deciding not to help other users out
- Continue rubbish/noise comments about Accept-rate values
- A general negative view or feel both for the site and the user
This is the core of your argument against showing accept rates. So consider this.
A low accept rate (defined as ~25% or lower) is indicative of one of the following:
- A user who does not know how to use the site.
- A user who does know how to use the site, but is either neglectful or malicious.
- A user who has not gotten good answers, which may be indicative of:
- Bad questions (bad questions can lead to bad answers)
- Lack of user interest in these questions.
A user who does not know how to use the site is a user who needs to be educated. Informing them of how accepting questions works is neither "rubbish" nor "noise comments". It is vital information that the user in question may have missed. Informing them of this creates a positive view of the site for that user (assuming the information was appropriately phrased. IE: not condescending or coming off like rep trolling). And some people don't want to waste their time with users who couldn't be bothered to read the FAQ; that's their right.
A user who is using the site neglectfully or maliciously is not a user who needs to be here. So I have no problem with seeing their questions downvoted and/or filled with "rubbish/noise comments about Accept-rate values" and/or not being helped. Stack Exchange requires give and take. There are responsibilities placed on the person doing the asking just as there are on the answerers. Someone who isn't pulling their weight is a drag on the site.
A user who has not gotten good answers due to asking bad questions is someone who needs to start learning what good questions are. Bad questions contribute "rubbish/noise" questions to the site, which is far more damaging than someone posting a comment on a question about accept rate. The whole point of the site is questions, after all; comments are just a supplement. And if the user who asks bad questions has a negative view of the site, then hopefully that will help them improve or leave the site. Either way, the site gets better.
A user who is asking questions that nobody either knows how to answer or wants to answer is generally unlikely to fall afoul of a low accept rate. The reason being that unanswered questions don't count towards accept rate. In low-traffic tags/subjects, you are more likely than not to have a few experts drop in to comb through them for easy accepts/up-votes due to being experts in a specialized field. In low-traffic tags, you get a disproportionately higher rate of answerers who know what they're talking about.
That being said, there will be some idiots who think they know what they're talking about and don't. It happens. But does it really happen 3 out of every 4 answered questions? I'd want to see some statistics on that before I can be sure.
So no, I don't see a problem per-se with providing accept rate information to users.
This all being said, I do wish that people would only confront someone about their accept rate if it is actually low (no, 65% isn't low). And they've looked through the question history and have seen something disconcerting (ie: good answers not being accepted). Most people who have low accept rates don't have that many answered questions, so it would only take a minute or two to look through their history.
However, the fact that some users are jerks about accept rate does not mean that having the accept rate itself is a problem. It simply means that some users need to be educated about what bad accept rates are.
The absolute most I would accept would be something where only an accept rate beneath a certain threshold (say, 40%) is shown. That way, you deal with jerks talking about people who are in good standing accept rate-wise.