3 questions (or 4)

[5jj]

I don't get this. Would somebody explain this? They are all correct sentences depending on the situation? Uhh..what situation?

The situation we are describing.

If something began to glow, glowed for a short time and then stopped glowing, I might say, " I should have seen it glow" or "I should have seen that it glowed.

If it glowed for some appreciable length of time, I might say, "I should have seen it glowing", or "I should have seen that it was glowing".

[Soup]

I don't agree that we have to consider it as a reduced relative clause.

If it were an isolated example, I would agree with you completely. However, in looking at all three sentences, I see a pattern emerging: reduction, which is why I would choose "glowing" over "glow".

I don't agree. I am a 'that' user, but 'I should have seen it glowed' is possible, if inelegant, in my opinion.

Fair enough.