So this just popped up on the Discord, there doesn't seem to be much of a consensus on what constitutes a sex act when it's not literally sex, or when there's no penis involved.
The post concerned is a breast sucking post (post #7843571), which, IMO, is most definitely an "explicit sex act", but because it's not listed under the examples in howto:rate there seems to be an argument going on whether it truly is one. It seems bizarre to consider groping (even minor groping) and very in-your-face breast sucking both as Q. I feel like this mostly stems from the fact that howto:rate focuses on hetero sex acts, but regardless, some line probably should probably be drawn.