Ah, there are several places in the code to be improved, but they have little effect individually, and little on Wakachan boards in general. The basic principle is that every "SELECT * FROM" without the help of an index is O(N), where N is the number of rows(posts). You can't throw it around casually unless your database is small. Which almost every board here is. It gets noticeable in the thousands.
The most glaring ones are where you do the select and then throw it away if a flag is set. Simple to fix. I'll go through it, but do you want them now or after the mythical next release?