I would salute the online family, and applaud them for their continued online presence and contributions for the whole week long. I would then, suggestively to encourage them, ask them to keep the fire burning!
I would then with a twist acknowledge and note the particular "seemingly eruptive post", pointing out its generalization, although a potential source for unwarranted conflict due to diverse misinterpretations.
I would then remind members that just as agreed earlier on at the beginning of the course, that I have always encouraged participants to contact me whenever there are any concerns to raise or if they experience any problems in the course and need assistance.
I would then beseech all members to exercise a bit of tolerant on each other and restrain from utterances that are likely to cause jitters among members. Reinforce the need to accommodate each others' flaws/weaknesses as a family and realize that we may not have similar qualities, as human beings are not the same.
Bring to the attention of all members the guidelines governing chat-etiquette (Relevance, Respect,Group-family, Peace, courtesy,) while emphasizing non-violation any of them as well as the need to consider and appreciate other peoples' feelings before making any controversial posts.
Privately contact the poster of the "seemingly eruptive post" to find out from them whom they consider " the really loud students who like to dominate discussions and then have the nerve to call those of us who prefer to observe and reflect a bit,before participating, lurkers"
Ask them to be tolerant as the course is accommodative of all paces of the participants.