One of the solutions pointed out so far is to go and restrain our set of tags to Portuguese names, burninating those in English (such as [tag:discussion]) and keeping a description in both languages. Initially, I agreed to this approach. However, when attempting to place myself on the position of a learner, finding the right tags may be a bit too tricky, and either lead to more poorly tagged questions or extra effort from other users having to correct them.

Since it's unlikely that these tags will form a semantic collision, I would suggest keeping them as synonyms, thus keeping it friendly to learners without crippling the purpose of tagging. This should also apply to different forms of writing in Portuguese (the Brazillian Portuguese [tag:sinônimo] and the European Portuguese [tag:sinónimo] are synonyms).