as explained, it is because it would block part of the flash, resulting in a shandow in the foreground in your shot.
the widest (without the wide conversion lense) on the 5500 is 37mm (35mm equivalent), which should be wide enough to take a take a wedding dinner table with the built-in flash (besides, the built-in flash would unlikely be enough to cover the full width with the wide converter).
going back future would reduce the effectiveness of the flash. further constraints is that the 5500 can only go upto ISO400.
last resort (short of buying a whole different system), you would then want to use to a slave flash... check out megaweb's post in this thread about his A70 + slave setup (megaweb - hope you don't mind).
Hi Thanks to Cactus jACK and LazerLordz for your advice. If without the slave flash, can i simply lower down the shutter speed and increase the ISO to compensate? Sorry for such a newbie question. Because i am afraid that carrying around the "L" Bracket around may seem abit bulky, and don't intend to invest on a slave flash so soon as i am still learning the basics of photography. Really grateful for you ppl great advices.
Depends on the lighting of the room. I've been to weddings where the ballroom is brightly lit but most are quite dim. Even if you increase the ISO, you may still get very slow shutter speeds and the only way round it is to use support like tripod or take off the conversion lens and use built-in flash.
as mpenza pointed out, it really does depend on the lighting of the room / area. ordinarily, jacking up the iso is an option (iirc the 5500 can only go up as far as ISO400). but you might still require mighty steady hands, pictures might turn out yellowish and grainy, and you must have cooperative subjects. also note the effective range of the built-in flash, it tends to be around 3m-4m only.
For me , "L" Bracket is not really bulky. If you think it is, you can handheld one hand to the slave flash and other hand to the camera. Sometimes I want to take a quick snap shots, usually I will use handheld method.