As mentioned by solstice258, doujinshi is one kind of self-published work that in the past was only sold in conventions in paper (nowadays they sell them in digital format too). Doujinshi can be completely SFW, and for advanced search you can either include or exclude them, but they cannot be excluded from recently added and the like because they are another format like Award Winning, 4-Koma or Long Strip. So it doesn't matter the format, even if you have Suggestive/Erotica/Pornographic unselected (unticked), you'll still see Safe Doujinshi. So no, you cannot exclude doujinshi from recently added nor lastest updates.