Kelly_E Questions right here within the announcement, rather than a Google form would be nice... that way they remain part of the record, so to speak, on the forum and are searchable way down the line (to let people know they might like to watch the recording).
It would be up to @Vladimir how he would like to do it, of course, if he wants to do it at all. But I would rather do it in Google Forms or something similar instead of just here, for multiple reasons.
1) Say person A is on a talk one week and gets a whole bunch of submitted questions. Next week, person B gets just one or two questions. That would probably not feel that nice for person B. If it's submitted so only Vladimir sees the questions, then he can just add his own, and it won't turn into a popularity contest.
2) I assume there are some lurkers here who don't want to post anything publicly. In a Google Form, they could submit questions, and then there could be an option to do so anonymously.
3) All questions end up in a neat Google Sheet, so it's easy for Vladimir to see them all, and he can combine questions that are similar. He can also skip questions that are unsuitable or not relevant to the conversation. (Probably not much of an issue now since the forum is relatively small with few active participants, but once it grows, he might get more questions than he can fit into one of these chats.)
To keep a record of what the talk was about, timestamps within the YouTube video can be added and posted here, along with the video link once it's uploaded.