Bill, it is not for me to say (I don't make the rules) but, generally 2 current posts by any individual should suffice and make it fair for all. In your example you could easily do two posts:
FS/FT: Tecra Laptop, Matrox G450 AGP, Packard Bell remotes
WTB/WTTF: Axis Network Camera, Matrox G450 PCI
In the Matrox case you can get people to look at it from two angles and some of the wording could be similar or the same. The exception I see could be with large ticket items (maybe a laptop like this) having their own thread so as to give it special attention. I could see that on items over $1000 but, there is no saying that it would not sell in a thread mixed with other items. I guess just using good judgement (which you appear to have after reading your posts 😉) is the best bet.
Just my $0.02