You can indeed, but I think I've posted exactly once to Main, it was over five years ago hence probably getting very few votes either way now, and existing votes on the post in question suggest that it would be very unlikely that five people would independently decide to downvote it in one day.

On the other hand, I've been hit by mass-downvoting more than once in the past, by a user who is widely (and with very good reason) believed to be active on LW with his (at least) third identity after the two previous ones were banned for downvote abuse.

The advantage of posting about it is that if indeed someone (whether or not the particular individual just alluded to) is mass-downvoting me, then they might be doing it to other people too, and some of those other people might see my comment and mention that it's happening to them, which might be useful to moderators if they're contemplating any sort of action.