Johannes Neumeier

To me personally this trend mostly speaks of a longing for the analog. Be it illuminated scripts with color decorations, carvings with inlayed color, or woodblock prints with layered impressions of different color, the current trend in these types (be in implicit sets to be used in conjunction or multi-color font formats) relives that tangible aspect of typography - which readers young and old alike have come to reminisce about. As such, I think it's worth cherishing these new forms as stylistic evolution.

From the point of view of designing type, however, I feel it's a gimmick. In the stylistic sense it is something that is easily recognised as trendy, and from a marketing standpoint innovators can thus claim new markets. Maybe it's because users of type don't feel confident (or can't afford to, in terms of time investment) to do these type of very graphic design laden experiments with type that they are comfortable with type designers picking colors and variations on their behalf - which makes this whole affair a tad bit more sad altogether.

Really good advice from the folks here. Thanks from my part for that.

This is vague, but my personal view anyway: You can think of a typeface as a person, someone with character, habits, quirks, manners, voice. I find it easier to imagine then which are ingenious and which are mediocre, and why so; which are interesting people to know and which will be shallow or boring soon enough.

And, please, take this humble learner's view with some critical reflection

In addition to the general sound advice already given, I also find myself playing around on letters that encapsulate the character of the typeface I work on. I don't mean to say start with something distinctive, but rather think of what are the essential features, and are there glyphs that really articulate those. But either way, always do basic n o H O's amongst the first.

Nina Stössinger said:

Belleve Invis said:

Recently many programming typefaces provides ligatures for operators, i.e., `!=` will be look like `≠`

Really? Is it just me, or is this terrible practice? 

Personally, I don't think it's a question of changing underlying data or whatnot. Have you actually asked programmers if they'd like it?

Staring at valid code patterns has a funny effect of burning itself into the brain, so substituting something as essential as a "!=" might actually be confusing. Scanning the code, using search & replace patterns, syntax highlighting... There's situations where you might be programming patterns that include the "!=" combination, but not as an "not equal", but as part of some string or other pattern. For example search all occurrences of "foo" followed by a space, followed by a "!=" followed by a space, followed by "bar" you might write as a regular expression like "/^foo\s\!=\sbar$/- your OT substitution is not context aware and will horribly distort the meaning and readability of a string like that.

It's great typographers turn their attention to coding, but substitutions seem like a very bad idea to me (as someone with a programmer's background). You are talking about an activity where mistaking "'" for "’" can crash your business' servers, or the difference between "!=" and "|=" makes traffic lights switch from red to green - don't mess with what people are reading and writing and leave them with their ascii.