No. Although it may be annoying, there is no rule in place regarding 'thanks posts'.
Example
With all due respect, I disagree;
Rule #1: Do NOT SPAM. We're not going to be TOO terribly strict with what spamming is, but if you deliberately post "Stupid Posts And Messages", we will warn you and if it continues, ban you.
I realize you have bigger issues than this, with the "database not available" and the increased traffic on AO and with that in mind, I think that a few of the newer users are using a "thanks" post to pump up their post count.
(I tried to use the "view all posts by" feature to find out if the few blatant offenders have posted any content other than "thanks" but that feature returns an error - The page cannot be found.)
I have never used the ignore list feature, but I will now add Happy7, pato65 and CR7 to my ignore list for their frivolous "thanks." Some other users may be added including THUNDER, CrazyT, funfunfunx, doctorpis, Starbow, etc.
I hope to be able to use the View Public Profile soon to confirm my suspicions.
While I may be guilty of not posting content, I try not to be a post whore.