Task Update/Feature Creep: We discussed this in our triage meeting and decided to remove limits from all keywords rather than continuing to add them piecemeal as people request them.
GrowthExperiments allows users to configure a list of templates that correspond to a certain article issue (like lack of links). Articles with these issues are then listed as tasks, with a hastemplate:tpl1|tpl2|... search query. Sometimes the list of templates is very long because the wiki subdivides articles with the given issue type into many subtypes (this is somewhat common with stub templates where many wikis have topic-specific stubs). This causes the search to fail (example: T279646).
It would be nice if templates weren't counted against the search length limit. hastemplate checks are simple index lookups so performance-wise such query terms are light, the change shouldn't threaten the length limit's purpose of preventing queries which cause performance issues.
(The issue can be worked around on the community side since hastemplate: searches templates recursively, so one can add a shared subtemplate to each template and search for that. So, this task is not that important. It would still be nice though and I don't think it would have any downside.)