Main reasons for rejections are, but not restricted to:
1) you seem to be a spambot advertising something, or
2) you are offering your own artefacts for sale (100% rejection rate), or
3) your comment is totally unrelated to the post it is supposedly commenting on and deflects discussion away from the topic;
4) While robust debate is acceptable, use of an overly aggressive tone and foul language intended to offend is not;
5) You are simply writing how much you hate me and my blog, and that I am an arrogant, evil extremist - and what you'd do if you met me in the street. This adds nothing to any discussion;
6) You are clearly a sock puppet (anonymous profile, hidden details for example) or impersonating somebody else, simply out to make trouble and waste time;
7) You are using the blog as a means to contact me with information or with questions, or asking me to remove something, and specifically ask me NOT to publish the comment (which I always honour);
8) Your comment deliberately or unintentionally gives away information which I suspect, or know from other sources, is sensitive (e.g., relates to something under investigation for potential criminal activity).
I prefer to know who I am talking to, if you have something to say that you think fit and proper to air in public, I do not see why you cannot do it under your own name. I write under my real name and frankly I do not see any reason, if they don't fall in the categories above, why others cannot do myself and my readers the same courtesy. If its worth saying, and you have nothing to hide, you can sign it with your real name.
Although my own posts here and replies to comments may on occasion be somewhat brusque or rough, I'd like to ask other commentators not to use the comments section of my blog to attack another guest here. I will not post what I see as personal attacks by third parties on other commentators. I have developed quite firm views on that due to my own experiences as a commentator on other people's blogs. Disagree with what was said by a commentator by all means, but ad hominem remarks addressed to a third party (or me) will most likely get your post rejected, take them elsewhere.
When comments come to me the return address is "no reply", so I cannot contact posters to tell them that I'd post their remarks if they'd consider changing the bit where (for example) they remove an email address or some other detail from an otherwise acceptable contribution to the discussion. All I can do in situations like this is reject the whole comment. I am prevented by the Blogger software from myself editing even a single word in a comment sent here, neither by somebody else, nor - annoyingly when there's a spelling mistake right in the middle - myself. The order in which comments appear under the post is the order when they are initially sent and not the order in which they were approved by the blog owner.
There is a word-limit to the comments section on these blogs. If you want to send a long reply (explaining something for example), it is best written in a separate document (Word for example) and copied and pasted into the comments box. That way if the system rejects it, you have a copy of the hard work writing a polite coherent argument and can try to repost it, split into several smaller chunks. But try posting it all in one go first.
If I am home, comments usually go up within an hour or so of sending. If however I feel the urge to write an answer (and, be warned, I often do), the comment does not get posted ('accepted') until the answer is ready. This is because if another reader comments on your comment while I am still writing, because of the way Blogger organizes them, their reply would then separate the original from my response to it and it gets complicated.
Finally I should say that this blog is all about freedom of expression, I have my opinions on a number of things dealt with here and since I live in a country where free speech is allowed, I therefore say what I think. Sometimes I make generalisations, sometimes I use specific cases to illustrate a point. In the latter situation it is only fair that the person or group mentioned ALWAYS have the right to answer and contest what I said - though I'd prefer them to do it in accordance with the 'house rules' set out above.
Thanks for visiting my blog, I look forward to hearing from you.