So we're having three "explanations" (but actually guesses) to that phenomenon: sandbox, penalty and "weirdness". Some people say they never got out of it, some say they did after 6-24 months. I've noticed some patterns when monitoring my affected websites too. My conclusion upon those three guesses is simple:
1. "Weirdness" is something people not really understand or didn't bother to get deeper into it. So I don't take it into account.
2. Penalty suggests we did something bad and big G punished us for it but we did nothing out of what we always do and usually don't get punished for that by G, so it's not a penalty either.
3. Sandbox seems to be a valid guess, although some people say it's a myth, and I saw it myself when my brand new website started ranking on page 1 for the main keyword within a couple of days so it's not THE sandbox people talk about either although we're talking about expired domains. (Still this guess is the most probable to my eye).
To the conclusion then:
It seems to be some kind of filter G puts on us to check if they can trust us and that is put on us only when we're using expired domains. In my experience, the two of my websites that got treated with this "filter" differed from my other websites (built the very same way - the same method) in two aspects only: they were slightly off the original topic which shouldn't be a big deal but maybe it is, and their backlink profile was significantly better that the backlink profiles of the best players in the niche. I instantly started ranking high and then G started suffocating the impressions for my websites and then they started disappearing to the command "site:" till they got to 4 pages even though none of them got deindexed and is visible when I type in their meta title using "" on G. Also those three pages change with time they're not fixed, (only the main page is always displayed to the command "site:"). On top of that, now G shows only 3 pages for one of my two affected domains. Also those three pages are usually those that get the highest number of impressions (which is still relatively low; around 10 per week) and like around 3 clicks a week in total, and the rest of the pages get no impressions or only like 1-5 a week. I got one of my website treated like that in the past but no site:4 effect for over three months and then it skyrocketed. That website was in the same category the original was but the niche was totally different (light art -> religious paintings) - it makes me think that that relevance maybe the key here not a strong backlink profile or maybe both are the factors. It may be also since G needs more time to calculate the power of our expired domain and to learn where they should place us in the ranking. So here we are, these are my two guesses, guys.
