What is the purpose of a translation? It could be either meant to make the text understandable in itself or to offer a path within the original text. The first option is the one implicitly adopted by most translations of Western texts into Western languages, but it presupposes some common background in order to be viable. On the other hand, the second option is the rule in most Indian and Western translations of Indian texts, which sound often awkward and display an unfamiliar English (or German, etc.). Be it explicit or not, their purpose is not to offer to the reader an independent text, but rather an easier path within the Sanskrit text. One reads them along the Sanskrit text and can, hence, better understand its syntax, avoid looking for the meaning of unusual words and so on. However, one does not use the translation as an independent text and one keeps on thinking in terms of hetu and dharmin, or of bodhicitta and upāyakauśalya. The technical translations of these terms (and of many others) immediately recall their Sanskrit original and often this recollective power is favoured by translators over the English (or German, etc.) shade of meaning. A well-known example is that of vyāpti (already discussed in this blog) translated as ``pervasion", although such translation runs the risk to convey the idea that the pervader (vyāpaka) is of smaller size than the pervaded (vyāpya). In such cases, the translation has, hence, the role a basic commentary had for Sanskrit students. It paves them the way into the text and it has no independent value. In order to do that, it is often more a metaphrase than a paraphrase, as it has already been the case with Tibetan translations of Sanskrit texts.
In sum, an independent translation of a Sanskrit text into a Western language is hardly possible, unless in selected topics, where scholars have already developed a common background (perhaps, some branches of linguistics or logic). Hence, if I am not wrong in this analysis, translators are bound to write a translation which plays the role of a basic commentary. However, basic commentaries are hardly enough to fill the cultural gap between today's readers and the Sanskrit authors. Hence, many translators have decided to add extensive footnotes, a line-to-line commentary, a separate commentary or a long introduction to the texts they were translating. Personally, I tend to write a separate commentary in the form of a long introduction because I am afraid that too long footnotes may hinder one's reading too much. Moreover I hope that the long commentary might provide the reader with the common background which will enable her to read the translation as if it were an independent text.