Yes doing a quick search [1] it's now apparently a more frequent error message for those trying to post show HN threads, especially if it's from a new account - so specifically the automatic filters are not liking your blog site.
Also your account looks like it's unused and you have not commented that much in that time - a guess is one of the algorithms used to filter fluff has taken that into account as well.
It is probably time to email the staff at HN for a bit of help. From what I've read, a little self promotion - proportionate though to other submissions, is ok - but it's got to be something that might be of interest.
Too many bot accounts just want to do promotion only and have near or no interaction with the membership at large which is why these additional filters have been introduced / tightened.