It depends with linking threads. If you're linking threads where you're giving an example of something funny (e.g. T-Rex) or directing someone who had a similar problem with relevant advice that's okay.
If a poster comes on and presents themselves in a completely different way to how they have done on another thread and gets unwarranted sympathy as a result or similar it's supposed to be bad form. For example if a poster is posting about what an awful parent her DP is and how much he upsets their children, but on another thread has posted about how they have deliberately driven a wedge between him and the children so he's never had a chance to parent you're supposed to report rather than link between threads.
Or for example you mention that one poster always takes a certain position on a particular issue and they deny it, it's bad form to link to examples of them taking that position.
BUT there is a grey area where a poster A says 'can you provide examples of me doing that'? The other poster B does so and then poster A runs off and reports the links even though they asked for them in the first place!
Mentioning no names eh A11 