I'm not the be all end all rules interpreter, but you have to register as a Blogger / Reviewer to be allowed to put links in sigs, at least according to rule #22d.
22. Links to blogs, e-cigarette review websites or
ecig-related blogs
a. All e-cig review sites or blogs must be checked by us before their owners may link to them from ECF. The owner must register with us in order that certain conditions can be checked - for example that affiliate links are declared.
b. To register, contact the Reviewers Manager via email - see the Contacts page.
c. Any blog or website linked to may require notification to us before the link is permitted, and this will always apply when the same resource is linked to frequently.
d. No signature links or 'siglinks' are allowed without registering as a Blogger. If you link to a website in your forum signature then you must register as a Blogger / Reviewer.
e. The type of website content or topic area is not relevant if it is in a siglink. All siglinks require registration.
f. An exception is allowed for pre-approved links, particularly those to consumer associations like CASAA. Links to national consumer associations, consumer activism groups, and local vapers groups are allowed.
There may be other rules that apply to non general members.
ECF Forum Rules