1) "kind (comparative kinder, superlative kindest)" Source and further information: http://en.wiktionary.org/wiki/kind#Adjective This, however, would only be a proof that the comparative form "kinder" exists... 2) According to the following discussion, both "kinder" and "more kind" can be used, the choice about which one has to be used depends on various factors. Generally speaking, "Whether a given adjective may take -er or more in a prototypical comparative construction is almost predictable.": "1. Introduction The prototypical comparative scheme, which is found in most (but not all) human languages, involves comparing two participants in terms of the degree of some gradable property relating to them. There are three basic elements: the two participants being compared, and the property in terms of which they are compared. Consider the sentence: 1) John is more famous than Bill. COMPAREE INDEX PARAMATER MARK STANDARD The participants are: - COMPAREE--that which is being compared, here John. - STANDARD of comparison--what the comparee is being compared against, here Bill. The property is: - PARAMETER of comparison--here famous. A prototypical comparative scheme will generally also include: - INDEX of comparison--here more (with a different choice of adjective it could be -er)." "2. Form of the Index of comparison We can exemplify positive and negative instance of the prototypical comparative scheme in English by: 2a) John is fatter than Tom. 2b) John is less fat than Tom. 2c) John is more intelligent than Tom. 2d) John is less intelligent than Tom. These are copula clauses with the Parameter of comparison being an adjective, in copula complement function. The positive Index of comparison is either a suffix -er/-[??](r)/, or a modifier more, /m:[??]/ or / m[??][??]/. There are corresponding superlative Indexes -est, /-[??]st/ or /-ist/, and most, /moust/. The negative index of comparison has a single form, comparative less, /les/, and superlative least /li:st/. " "3) [ILLUSTRATION OMITTED] An Index of comparison may also be preceded by an adverb such as even, simply, really, or kind-of. When used in a prototypical comparative construction such as (1-2), with two participants and one property, some adjectives only take -er (for example, big, kind), some only take more (intelligent, beautiful), while others may take either (friendly, stupid) as the Index of comparison. When two properties are compared with respect to one participant, in a non-prototypical comparative construction, we get: 4) Mary is more kind than intelligent. One cannot say *Mary is kinder than intelligent. That is, when the first adjective in a construction like (4) is one which would normally take -er (or an irregular comparative), it must in this context take mope. This is discussed further in [section] 3. (Note that whereas the prototypical comparative construction is found many language, a non-prototypical construction such as (4) occurs in far fewer languages.) Whether a given adjective may take -er or more in a prototypical comparative construction is almost predictable. (3) It depends on a combination of factors: --the phonological form of the adjective, --its frequency of usage in the language, --whether or not it refers to a property which is, in a logical sense, gradable. " Source and further information: http://www.accessmylibrary.com/coms2/summary_0286-15305111_ITM