azhong wrote:Q1: Does down the long table mean something like along the table or following the table? If so, can I say up the table instead?
It means "from one end of the table to the other". It emphasizes that the table is very long and Yaxley and Voldemort are at (or near) different ends of it, far from each other even though they are both seated at the same table, with a lot of the table between them. This construction can be used with anything that is especially long: "he looked down the long hallway," "he looked down the long corridor" etc.
I don't think it would be ungrammatical but it's not common to say "look up" in place of "look down". Maybe this is because "look up" is also a phrasal verb on its own, with a different meaning. However, you would use "look up" in a sense similar to your example if you were talking about something that was literally up, like "he looked up the long stairwell" or "he looked up the long elevator shaft."
For tables and corridors I'd stick with "looked down".
azhong wrote:Q2: A Confundus Charm, does it mean a person named Confundus Charm? If so, I guess it's an oral expression, being informal, even ungrammatical?
No, Confundus is the name of a charm (= magic spell, incantation) that has been used against Dawlish. "Confundus" is a made-up word here but because of its similarity to words like "confuse" and "confound" (and Latin confundo or Spanish/Portuguese confundir for us language geeks), it's meant to be obvious to most readers that a "Confundus charm" is a magic spell that causes its victim to become confused or disoriented. So this is what happened to Dawlish: magic was used to make him become confused.
It then says "he is known to be susceptible" which means that he tends to have these magic spells or charms placed upon him quite easily; in the context of Harry Potter this probably means that his own magic is not strong enough to protect himself from becoming a victim of these charms.
In a more normal (non-magic) context we'd says someone is "known to be susceptible" if were talking about disease, for example, we might say that someone is "known to be susceptible to the flu" or "known to be susceptible to pneumonia". It means that person tends to become sick with those illnesses more easily or more often than other people do, and has had those illnesses several times already.
azhong wrote:Yaxley had leaned forward to look down the long table at Voldemort and Snape. All faces turned to him.
“My Lord, I have heard differently.”
Yaxley waited, but Voldemort did not speak, so he went on, “Dawlish, the Auror, let slip that Potter will not be moved until the thirtieth, the night before the boy turns seventeen.”
Snape was smiling.
“My source told me that there are plans to lay a false trail; this must be it. No doubt a Confundus Charm has been placed upon Dawlish. It would not be the first time; he is known to be susceptible.”