In the 2015 community ad proposal thread, I posted an ad for physicsoverflow. Then I posted a comment under it to provide some extra information. Here I'll try to reconstruct the deletions in chronological order from memory, if there is anything not factual, I welcome corrections:
First time I commented
I'm surprised by the number of downvotes, in case of misinformation and with no intention to start a debate, here's a mathoverflow link containing a brief introduction:https://meta.mathoverflow.net/questions/1608/physicsoverflow-just-went-live
The above comment disappeared when I checked the page a few hours later, and I assumed it was an error, so I posted a comment again
This got deleted again. So I made the inquiry
I'd like to know in accordance to which rule my comments got deleted twice with no notification, whereas for other ads some comments adding information are perfectly ok.
This time I monitored my post, and this inquiry got deleted in a few minutes after I posted it.
Hence here I'd like to use this meta post to make a formal inquiry:
(1) In accordance to which rule my comments got deleted thrice?
(2) Is it common practice for moderators to delete comments without notifications to the author? Is it justified by any policy?
Followup: According the answer by David Z and Kyle Kanos, the reason is Qmechanic posted a link and asked people not to discuss under the ad. To defend myself I must say I did not ignore Qmechanic's comment, the reasons I posted my comment despite it are:
(1) Qmechanic's link is not the mathoverflow link I gave, and I do think mathoverflow information has more merit since people there are more experienced with a research-level site. And if my memories serve, originally Qmechanic did not post the link of the PSE meta post and only the chat room was given, only after the deletion of my first comment did he post the link of PSE meta post. Please correct me if this is not factual.
(2)I did not consider my link to be a "discussion", but only an announcement. But I won't tangle with you on this, I am willing to follow your definition of "discussion" and let it go.
(3)To me notifications have usually been given before deletion on PSE, but now I know that's out of courtesy, and I guess there's a difference between the PSE main site and meta. I'm fine as long as it is written in the rules, thanks for the clarification.
After the clarifications, now what makes me curious is why my ad deserves the special treatment? That there is no such mandate like Qmechanic's imposed on other ads?
Addition: After the conversation with Kyle Kanos, it becomes clear that moderators are not violating any rule set by Stackexchange; what is also made clear is that moderators have unlimited power at comment zone with 0 restriction, in accordance to the rule. This is a very unjust rule, and it would be humane for moderators to refrain from wielding this power. However, the current situation suggests the unreasonable(but again, not illegitimate) power is being very actively exercised. I rest my case.